A rental on Sanibel/Captiva might be good except you will want to stock up on groceries before you go over the bridge to the islands, they have groceries but overpriced/limited selection.

The Marriott on Marco Island has a fenced baby pool ringed by loungers and landscaping, on the beach. The other two outdoor pools are also really nice. I remember telling my DH it was too bad the kids were so big because the baby pool has the best view of anywhere on the resort grounds.

We are looking to take a vacation with our 18 month old in February. Any suggestions of places to go? Looking for something nice (but no more than 750/nigh) that is still somewhat family friendly.