Regarding CheapCaribbean.com - Awesome company, great personalized service (ask for Keith). You need to specify top 5 choices, but if you pick Royal Palm, Atrium, Pelican, Flamingo, you are practically guaranteed to be in the right area. It is probably more economical to go for 2 weeks with them at 499/wk than paying hotel rates for the 3 extra nights.
Good Luck!
Forum:
The Friendly St.Martin Island Forum