We've chartered twice out of Oyster Bay and a lot more in the Virgin Islands (US, British, Spanish). The winds might be higher in the St. Martin area, but it's not that far from the BVI and a lot of your sailing will be on a reach, say between St. Martin and St. Barts.
Agree with speciald about provisioning, given your short time aboard, and you should plan on eating dinner aboard more often than not. Given your 5 day schedule, and assuming the conditions are not too rough, you ought to visit Orient Bay and spend a day on the beach. We prefer the Ile Pinel anchorage for snorkeling and staying overnight, but the Green Caye anchorage is more convenient to the beach. We'd recommend you approach the beach in your dinghy at the south end of Club Orient to avoid a shallow reef.
Grand Case is a must for the fine dining. There are so many choices, so you'll need an hour or so to check out the menus. You'll also need to use a stern anchor for your dinghy, assuming you are coming in at the pier.
Marigot is interesting ashore, but we've not been tempted to stay there overnight. Going in the other direction, you might stop at Ile Fourche (uninhabited, but you can hike there) and/or Columbier on St. Barts proper. You'll be eating aboard in either case. Columbier has a hiking trail over to Flamands beach, which is worth the time. If you go on to Gustavia, you will likely anchor in an open area and dinghy in to check in with the Harbor Master and pay an anchoring fee. I think its worth the bother. You can also get an original Cheeseburger in Paradise or have a nice dinner elsewhere.