With a 10 year old I would choose the Dolphin!
We have stayed in both but find the Dolphin has more of a family feel. You have the 24 hour food court with Picabu- the fountain with ice cream and burgers and the candy shop as well as the arcade and laundry!
Also if you and dh want a meal alone you can have two hours of free child care at the dolphin club - and out of all the WDW childcare clubs it was my dd's fav along with neverland and AKL. We didn't use them much but my kids loved them as much as dh and I love having a couple hours alone during vacation.
The pool is great and shared by both hotels and there really isn't much difference in transportation so that's a wash.