The beach that far south is really nice. The water is shallow a long way out, and there is sea grass if you walk into the water. However, it is easy to swim off a pier. It is also easy to put on a pair of those water shoes, if the sea grass bothers you. I can't imagine that the seagrass would deter 2 teens that want to get in the water.
Sunset has a nice pool and very nice grounds. I have never stayed north, so I can't comment on that. Are you looking into anywhere specific north?