I second KristMc's recommendation for Soualiga Destinations. We stayed on St. Martin for a week last April and spent a day with Capt Brett of Soualiga Destinations. There were 7 of us (including two 11 year olds and a 10 year old) and we all had an amazing time! We were on the Random Wind the year before and loved that experience as well, but I give Soualiga the edge because you get to see much more of the island.