I recommend going in the afternoon and doing something else in the morning like shopping or butterfly farm. We had 7 kids under age of 6 and never felt uncomfortable. However, it is a St. Maarten beach and topless bathing is allowed. There's plenty of room to spread out.
We hung out at the sunset beach bar, but we were concerned by their website which shows some topless women (
www.sunsetbeachbar.com). However, there weren't any at the bar and we only saw one topless lady on the beach at a distance. I've got a friend who lives at St. Maarten and she says that the bar is actually pretty family friendly during the day. I guarantee that my wife and mother would have been the first to grab the kids and move on if there were blatent college type activity going on.
As mentioned, I'd recommend going around 2pm and grab lunch at Sunset Beach Bar as the big planes come in between 2 and 4. They then depart between 3:15 and 5:30. HOWEVER, there is tremendous traffic and a drawbridge that goes up at 5:30pm for 30-45 minutes to add to the congestion, so if you're driving yourself, you should probably leave no later than 4:15. We waited for the 747 to take-off at 5pm, got stuck at the drawbridge and just barely made the ship departure time of 7pm (and we had a local friend as a guide). If it were me doing it again, I'd take a taxi and arrange a time that the taxi driver feels is most appropriate.
You've probably seen my videos, but here's the link:
http://www.disboards.com/showthread.php?t=737033&highlight=747+video