Camber Sands is terrific if (a) you are under 20 and fit or (b) you have obedient dogs with excellent recall! The tide really does go out for miles. When it is in, it is not possible to swim because the water is only about 10" deep, if that. Very flat. Also the local authority increased the parking charges last year to an astronomical level. I think it went up to £35.
Rye is lovely (but hilly) but as previous posters have said - wear sensible shoes! A couple of years ago the local council wanted to concrete over the cobbles for elf and safety reasons. There was outrage, oddly enough!
The other option, of course, is to go to Rye and have a splendid lunch in the Mermaid Inn!!