The Build includes a new children’s wing, which opened in February 2025, with work to refurbish and extend the rest of the hospice expected to finish in spring.
New facilities will include a hydrotherapy pool, a wellbeing suite and an education centre.
Holdsworth said: “Our building had fallen behind the quality of our care.
“The Build will not only bring our facilities up to date, but ensure that we can continue to support thousands more families for decades to come.”
Fundraising events included a zip wire challenge at Xscape in Castleford, with a “Raise the Roof” donation drive in September raising more than £400,000 in 36 hours.