Jimisue,
If you're looking for another 'higher end' restaurant for a great lunch and a perfect day at the beach, although it's about as far away from the Dutch side as you can get, you might also try the Restaurant at Anse Marcel (there may be a more formal and official name for it, or that may be the actual name), on the same stretch of beach as RIU (formerly the Radisson and before that, perhaps L'Habitation?).
We had been hearing about it from a lot of different sources and tried it ourselves in April and it was lovely. That cove is completely protected so there are no strong waves; the beach is find powdery white sand; the beach service is very good; the restroom facilities are very nice, clean and well maintained; and lastly - the food is yummy, too.
The experience of getting there is half the fun and you sure do get to see some scenery along the way but once you come down the hill into the property itself, at the guardhouse turn left and keep driving until you can't drive any further along the road and you will run right into it.
The only thing I could remotely find to say in the negative is the chairs are not free with meals, or were not when we were there, but they are so comfy and everything else is perfect so in the end, that was okay, too.