Pay Dirt is Slate’s money advice column. Have a question? Send it to Kristin and Ilyce here. (It’s anonymous!)

Dear Pay Dirt,

Hearing stories of my mom’s travels in the Air Force before she had me, it was my dream as a kid to see all seven continents before having my first child. In my 20s, I traveled frugally; a scholarship brought me to Europe and South America. I got engaged in Asia, honeymooned in Africa, and did a babymoon while six months pregnant in Australia on my husband’s work travel points. It all seemed doable until I found out that setting foot on Antarctica alone would cost at least $10,000—and far more if I want to go with my husband. We decided to defer the last continent until much later, but didn’t make any tangible plans.

Now I’ve noticed that Disney has an Antarctica cruise. As a hostel/couch-hopping, public-transportation-taking Millennial, I’ve always thought Disney-related travel was unjustifiably extravagant, but apparently I’ve become soft in my slightly older age. because I’d like to try this luxurious option! In about 12 years, I’d like to take the trip with my husband and two kids to celebrate our 20th anniversary and the kids’ high school graduation (big assumption that Disney will still be doing this trip then, but I am guessing alternatives will still exist if not). My target is to save about $50,000. Is there a good way to invest this money as I’m socking it away, especially since I don’t want to touch it for at least a decade anyway?

—Not Quite Frozen Assets

Dear Not Quite Frozen Assets,

Funding a trip to Antarctica is certainly a luxury, anyway you go. I couldn’t find details about the Disney cruise you mention in your letter but I took a look at a few other cruises being offered and the cost for a family of four today is about $10,000 per person, but could cost as much as $50,000. Assuming a 5 percent rate of inflation for these cruises, you’d need to save between $36,000 and $72,000 just for a budget cruise. You’ll also need to save for the other costs involved, including flights to departure ports (Ushuaia, Argentina or Punta Arenas, Chile), pre- and post-cruise hotels, optional activities (like kayaking around the glaciers, if that isn’t included), gratuities, and other onboard expenses. All in, a budget trip could balloon to between $90,000 and $110,000.

So, how do you invest for a trip of a lifetime? While 10 or 12 years seems like a long period of time, it’s just a blink of an eye when it comes to raising a family and investing. You’re on the cusp of what I would call a longer-term investment, which is typically more than 10 years.

When you need short-term money, say within five years, the safest bet is to put it in a high-yield account, where the financial institution is a member of the FDIC. While you might not earn more than 3 to 5 percent, it’s a safe bet that you’ll have the cash (up to $250,000 per social security number) when you need it. If you’re investing for more than 20 years, say for retirement, then you can take a risk by investing in the stock market, knowing that the total amount could be lower or higher, but the S&P 500 has enjoyed an average return of 10.8 percent per year.

In your case, consider splitting the difference. Keep half the money in a high-yield account and put the rest in a couple of index mutual funds.

If saving more than $100,000 in a dozen years seems out of reach, consider pushing back your timeline. Another option is for you and your husband to enjoy this experience on your own and take your kids to a different, less expensive part of the world.

Please keep questions short (<150 words), and don‘t submit the same question to multiple columns. We are unable to edit or remove questions after publication. Use pseudonyms to maintain anonymity. Your submission may be used in other Slate advice columns and may be edited for publication.

Dear Pay Dirt,

I have an unusually good problem, but am flummoxed by how to deal with it. My son, who just started high school, receives Social Security survivor benefits every month (I’m a widow). The money is supposed to be used for his care, but I’ve been able to save almost all of the money, and it is getting to be six figures. Assuming he is going to college in about four years, what’s the best way to invest it? (It’s currently sitting in a credit union savings account with a low interest rate.)

—Good Problem

Dear Good Problem,

I’m sorry for your loss, but I think your son is so lucky to have a mom who has been able to manage so well on her own. Well done!

There’s a short-term and longer-term answer to your question. The short-term answer is easy, so we’ll start there. Since you don’t need the survivor benefits for your son’s care right now, you should immediately move all of the funds into a high yield savings account. You can find a list of online options at Bankrate. Make sure you use an institution that’s a member of the Federal Deposit Insurance Corporation (FDIC), which will insure your deposit up to $250,000 per social security number.

You can leave the cash in that account to accumulate while your son is in high school. The question I have is whether you’ve done an adequate job saving for his college education. Given that college is just a few short years away, if you’re going to need this money to pay for his education, you might want to leave it in the high yield account, and draw it down as you need it. You could also look into laddering short-term bonds, which might pay a little bit more interest.

Help! I Want to Carry on a Sweet Family Tradition. But My Sister-in-Law Says It’s Unhealthy.

My Husband Pushed Us to Live Closer to His Family. Now He’s Complaining About the One Thing I Ask for in Return.

Help! My Biological Family Wants Me to Cut Out My Adoptive Mother. I’m Torn.

My Sister Squandered Her Entire Inheritance. Now She’s Chipping Away at Mine.

If you have college funds set aside or have already started a 529 plan, great. If not, consider whether your son is college-bound and if this would be a good way to fund some of his tuition and save money on taxes. You can get more information about 529 college savings plans and what is offered in your state at collegesavings.org.

If your son is not college-bound but is instead headed either for a trade school or perhaps some other form of work, you can continue to save the money. But, you might want to think about what a longer-term investment would look like, so that he has the money for a down payment on a home or to start a business. Dividing the cash into low cost index mutual funds is an easy way to diversify, and a basket that includes an S&P 500 index, a total bond fund, a small cap index fund and an international index fund should produce a higher return than your high-yield savings account, although with slightly more risk.

You might want to pay for a couple of hours of time from a fee-only Certified Financial Planner (CFP), who can give you a comprehensive financial analysis of your health, along with some advice on how to handle this money going forward to support your son throughout his life. You can get matched to a few CFP for free from the Certified Financial Planning board at CFP.net.

—Ilyce

More Money Advice From Slate

We have two daughters. One was married, but after two years of marriage, her husband had the rug pulled out from under him when he found out she had been having an affair for seven months. We dearly loved our son-in-law—a person couldn’t have asked for a better human being. He was totally devastated, as we all were. This daughter and I have always butted heads—we are like oil and water. I can’t say or do anything right, and she truly just does not like me. I am seriously considering changing my will to the one daughter 50 percent, the daughter who doesn’t like me 25 percent, and ex-son-in-law 25 percent.

The latest sex, parenting, and money advice from our columnists delivered to your inbox three times a week.