Theres a few choices here, but the priority should be, get mortgage 1 balance reduced, as its your highest loan interest rate, keeping the term the same, so improving cashflow as Sarenco highlighted.
Personally, i would not use all of the 25k to pay down mortgage 1, but, work out (try at least!)how much your college expenses will be in 2020 & 2021 put that 2 years expenses away, and put the balance against mortgage 1.( no reduction in term) In the meantime, the improved cashflow, needs to be ring fenced, for college expenses in 2022 and beyond. The 2 years put away + improved cashflow once mortgage 1 is reduced, gives comfort.
Review everything next year, as when you turn 50, the max pension & avc combined, % limit increases to 30% of gross earned income.