If most of the guests are coming from Europe, they are unlikely to come to St Thomas. Most likely will arrive Beef Island via Antigua, although other routes are available.. Flying via the States generally works out a little cheaper but takes considerably longer - unless they are staying with you or other friends/relatives en route. Very, very easy to collect from Trellis Bay.
The most important thing is to talk about it all in advance so everyone knows what to expect : they should be aware of cabin size, number of heads, fact that noise travels easily, maybe you like to make the most of daylight and don't appreciate people lying in til mid day, sharing washing up (no dishwasher) and maybe couples take turns to prepare and cook meals. Stuff like that can make a lot of difference if they aren't sure what to expect.
You will have a great time if everyone is relaxed and easy going.