If possible rent at least 2 of the vehicle fleet you will need on STT and designate them as cargo for a provisioning trip to CostU less in STT - you will surely save $100's of dollars over STJ shopping.
If you are planning any dinners out as a group I would recommend making those reservations asap- many of our restaurants are small by stateside standards - maybe consider having a chef do a few evenings at wherever you are staying. Good luck with the planning and you should consider event planning as a possible career move if it all works out!