With that location, they are going to be spending a lot on cabs, for sure.
The Anse Marcel Beach Caf�/Restaurant, at the other end of the beach from the Riu, is excellent. They can walk the beach to get there. The Jam Rock Caf� back out on the "main road" is good; local Caribbean food. Ti Bouchon is highly rated although I've never been there when it was open (I go in June). There's also a pizza place on the main road that folks say is good, although I've never eaten there either.