More suggestions. For both you can fly to Ft. Lauderdale. A smaller airport than Miami, but big enough to have services, yet much more pleasant, and less waiting.
1. A Caribbean cruise. With 3, 4, or even 5 port stops at locations good for diving. During those port days you can go to beach while waiting for him (bring a walkie talkie or cell phone so he can find you), or can stay on ship with lots to do.
2. Florida Keys. Key Largo (and others) has good diving. You'll find good food, maybe not many good beaches. But it'll be quiet and enjoyable.
While not diving, Miami South Beach has lots of good restaurant and amazingly cheap lunches. Key West is always good for a 1-2 day visit.
Prices are coming down even more due to the economic situation.