By "mobility disabled" do you mean wheelchair? If so, I'd suggest Contemporary Resort. On our last trip to WDW we stayed at CR and 2 weeks before the trip my husband fell on the ice and broke his ankle and was in a wheelchair for our trip. It worked at so well at CR because of the ease of taking the monorail and not having to travel far within the resort itself to get to our room (we were in the tower). I love the WL but we found out one night that the smaller boat transportation back and forth from WL is not wheelchair accessible -- only the larger boats (ferry-size) are. And while the bus transportation usually worked out fine for us there were 2 times when we had to wait for the next bus because there was already one wheelchair passenger on the first bus -- the buses each only have one secure riding position for passengers in wheelchairs. I also love the Poly but would not have wanted the walk to the longhouses although if you asked for a longhouse closer to the main building that might be OK. Same reasoning for GF. As for the other deluxes, if you think you'd be spending more time at MGM and Epcot than at MK, then BC (awesome pool) or BW (awesome pool slide) could work but some of the BW rooms are VERY far from the elevators. And as for AKL, if it's the kids' first trip, I'd go for a resort closer to the other three parks and for someone with difficulties with mobility, AKL is just far from everything and you'd need to take a bus everywhere.
So for all the above reasons, I'd go with CR - tower room.