Hi ndcurry, welcome to Cruise-Chat. I was hoping someone would have answered your question by now. We've been to St. Maarten a half dozen times, and I hate to admit it, but I have never heard of Grand Case. I did find this
on the web. It looks like a very beautiful beach. I hope this site is a little help and maybe someone has actually been there that can help as well. Best wishes on your upcoming cruise!