I am just going to chime in and say you may want to seriously reconsider Windward Passage. And if you do stay there, please don't walk around after dark!

As for your return trip, I would be apt to take the 8:30 from west end if you are going to be there anyway. The taxi ride from WE to Roadtown (to get the 10AM) isn't exactly quick so you won't actually be saving a whole lot of time in the grand scheme of things (and paying for a taxi). After clearing customs in St Thomas head over to Glady's for a big breakfast (airport food there is crap choices and super $$). Do a little shopping before heading to the airport. No stress and you have a back up plan with the 10AM if you miss the 8:30.
Don't even consider the 11:30. Too close.