I am going to the caribbean in May and have booked 3 tours at locations that you mentioned. Although I haven't done any of these yet, this is what we booked so far:
St Thomas - we are sailing on the Winifred. I have read good things about this tour on this board and cruise critic
Antigua - we booked with Lawrence of Antigua. Got his info from the boards too
St Lucia - booked the pirate ship (Brig Unicorn) through RCCL
Have a great time.