Welcome to iRV2. Being your neighbor (Wellington) I understand the question. It all depends on how far is too far and how much do you want to spend. Gut feel says anything north of I4 is too far. The same distance south puts you in the Keys. Not knowing what the kids have already seen, consider:
2. WDW and area
3. Lego land (central Florida) LEGOLAND Florida - LEGOLAND
4. Directly west to Myakka state park Myakka River State Park - Home
5. South 150 miles gets well into the Keys. There is quite a bit to do in Marathon. There are several CGs to choose from.
This should be a good start. If you want more ideas, post here again.