sethgold

Another vote for the Philippines:
http://www.divecamiguin.com/

I check my housing, strobes, ports, etc. in a Pelican "steal me" case. I've been to Cancun, Curacao, Honduras, Philippines, and Cayman with zero problems.

In low light the Canon 100mm has a hard time focusing. In these situations a manual focus port is very helpful.

My wife and I have been dragging our kids (now 8 and 13)  on dive  vacations for 5 years. Here are my suggestions, from best to worst, given your constraints.

If you'll only travel on Frontier, fly to Cancun, rent a car, and drive to Akumal. Very easy diving, close to Maya archaeological sites, very low key and safe, pretty reasonable, turtles hatch in the summer, no day care or organized activities.
http://www.locogringo.com/akumal/
http://www.akumaldiveshop.com

If you want an all-inclusive place that's great for kids go to Anthony's Key in Roatan Honduras. Your kids will love it and the diving is better than Akumal. You have to fly Continental or Taca.
http://www.anthonyskey.com/

If your 12-year-old changes her mind about diving, and you decide to blow off your frequent flier miles and your budget, this is the way to go:
http://www.kidsseacamp.com/

I think we all enjoyed Anthony's Key the best out of those three trips.

I hope this helps.

Move to the Phillipines.