Let Moorings provision the boat with the staples, commodities, drink and water, then taxi to Grande Marche for the things you actually want to pick out yourself. Will save you a ton of time and trouble and the extra cost is little more than a rounding error in the total cost of the trip.

A day up in Anguilla is worth it but I wouldn't bother with St Barts if you're doing the usual 7 days. On the last night, anchor in Orient for an easy sail into Oyster.