As a SoFLA girl...I can say that you and your family will have a good time if you stay anywhere from Boca Raton to Miami.
I personally suggest that you check out these places...
Fort Lauderdale beach area--there is diving, golf, beaches, shopping, boutique stores, museums, great restaurants on Las Olas, and is an all around great place in a central location. It is also within driving distance of Key Largo for a day trip (about 1.5-2 hours each way).
Miami / Miami Beach--also has diving, golf, beaches, shopping. It is a bit more upscale if you plan on staying right in Miami Beach (South Beach). It is also much closer to Key Largo and makes a day trip there pretty easy, too (about 1 hour each way).
There are also nice areas in between Ft.Lauderdale and Miami, like Hollywood Beach.
Deerfield Beach--again..golfing, beaches, shops, restaurants. There is a Howard Johnson's right on the beach. This puts you near Boynton Beach and I hear they have really good diving, but I have no personal experiences, yet.
Key Largo will be tough for your family if they don't dive...
I will say that if I had to pick, I would pick Ft. Lauderdale because I am biased.

I just know that area really well and love it! You have lots of options right on the beach or a 10 minute drive puts you in Las Olas with a lot of shops/restaurants nearby...there is even an IMAX theater in the area.
Last thing, go to the
Florida Conch Divers area of the board. It has lots of info! Search some old posts and I would post the question there. Others will have lots of info. Once you pick where you are going I would ask everyone to recommend a Dive Op...make sure you give specifics about the type of diving you want to do and you skill level.