Welcome to cruise-chat.
When looking at 4 or 5 night cruises from Florida you are limited to either the Bahamas or something which goes to Cozumel and one other port such as Key West or perhaps Grand Cayman.
With three adults (I consider teens as adults for space purposes) you need to look at a cabin with a convertible sofa as the third bed. This is often the case for balcony cabins depending on the cruise line and the ship. Older ships rely more on pullman beds (single bed that pulls down from the ceiling) for the third berth, and these are really only suitable for children.
Price is very subjective. The cruise fare is part of it, but the onboard charges can add a lot to the bottom line. You have to pay for all soft drinks, alcohol drinks, tips for the crew, specialty coffees and desserts, and if the ship has specialty restaurants they have a fee too. Tours are extra, and it depends on the tour as to how much you will be paying.
Carnival and Royal Caribbean are the two major players for the 4/5 night Florida market when it comes to having the most ships and choices. Actually, for next April Royal Caribbean has a really nice ship (Radiance Of The Seas) cruising out of Tampa. The Celebrity Century is also doing short cruises. The Century is a personal favorite ship.