there is a TON to do in Vegas for all ages ... go in April/May or Sept/Oct to avoid the heat/cold.
Lake Mead is awesome, not being able to swim is no big deal, the banks are mostly shallow so you can wade around, there are boats and jetskis for rent. Hoover Dam. Mount Charleston. The whorehouses in Pahrump
Many of the casinos have bowling alleys, movie theatres, video arcades, etc. They mostly ALL have really incredible swimming pools. Some have huge shark tanks, dolphin pools, tiger cages, and so on.
I miss it terribly