D.S.
We stayed at the Bahia Mar four years ago and it was nice. Very reasonable, clean, nice pool ... only issue is, like most hotels on the beach side, you have to walk a bit to get to the beach. Depeneding on kids age(s) that could be an issue with how much stuff to carry. They did have condos available as well, that are closer to the sand, but I don't really know anything about them. This year we were planning to go back and stay at the Sheraton but my friends were there visiting and called to say a 30+story building was going up and it was REALLY noisy and lots of dust flying. We cancelled. We are though going to Corpus, with kids, in August and staying at a Quality Inn, on the beach. Not fancy at all but VERY reasonable, they have suites rooms, and it includes breakfast... also a lot less driving and with $4/gallon gas - this is a better thing for us.
Good luck and have fun.