While it's not warm water ocean diving, Lake Phoenix is good for gaining more experience. It would be good for the kids as there are a lot of sunken artifacts in shallow water (basketball hoops with a bowling ball for dunking, carousel horses, a school bus among many other things).
My fiance and I use it when we haven't been in the water in a while and are preparing for a dive trip. Below 25 feet can get pretty cold, but above that it's usually pretty warm during the summer.
That's where our youngest is getting certified. He is there today with his SCUBA camp and the rest of us will join him tomorrow while he finishes up his certification Looking forward to it!