If it were me, it would be either the Contemporary or the Boardwalk.
Both have great locations: -
CR: Walk to MK; monorail and boat to WL/FW.
Boardwalk: Walks to Epcot and Hollywood Studios and, well, it's on the Boardwalk!!
The pools would be good for the two of you. Two to choose from at each resort and good for kids who are too old for splash pads, but not quite ready for the BC/YC pool. The BW slide is supposed to be the best and at the Contemporary, you'd still have a pool right by the lake (like at the Poly).
At the CR, you could opt for the Garden Wing, so it would be easy to hop back and fore to the pool and to enjoy the lake setting and watch the Water Pageant. Or you could splash out on an MK view in the main building and watch the fireworks from your room.
At the BW, you wouldn't be in too spread out a resort and you'd have all the fun and eating options of the Boardwalk and Epcot on your doorstep.
Good size rooms at both resorts.
Now I've written all that, I want to come, too!