We really enjoyed St Martin or Sint Maarten, whichever one you call it. I think it has to do with whether you are on the Dutch or French side. Royal ported on the Dutch side. The port area here is not terribly big but not too bad. There is no Senior Frogs silliness but a small bar is there for drinks and later in the day a few frozen drink stations pop up. Shopping overall is pretty decent here, even in the port area if you haggle some. My wife picked up a new wedding band for about half what it would cost in the States from one of the guaranteed vendors in the port area. That was of course after haggling a bit and letting them know we would go to look in town. There is some pretty darn cheap "St Martin" branded rum in the Duty Free shop there. I'm talking 2 liters for $11. We didn't get any but I was tempted for mixed drinks.....
If you are going to shop, you will really want to head downtown. The cruise port terminal is located a bit away unlike most ports. You will want to either take a Water taxi at $4 each way or Walk. Taking a land taxi to downtown is not cost effective. Once downtown, you will have ample opportunity to arrange for a taxi. You can tell the driver when you want to be picked up at each location and they will be there waiting. You can negotiate the price some for the whole group but not much.
The shopping Downtown is very nice. There is a white hotel or something a little to the right of where the water taxi drops you off that has $3 rum punches. They were pretty good but I doubt they lived up to their claim of Best on the Island. The main street right off the beach has mostly jewelers and more expensive shops. I found a place across that street from the place that sold the rum punch called Caribbean Outfitters that had cold poweraids for $1.25 each.
The main road that runs parallel to the beach is the one with all the jewelers. The locals shop a little further from the beach and on the main road that runs perpendicular to the beach is where the locals shop and prices come down a bit.
We decided to go to Maho beach (Also known as airport beach). Our driver (Tony) was very nice and did a little of the tour guide thing as we drove there. The beach was nice but a bit eroded. There are bars at each end of the beach and we stayed a the one by the Taxi drop off. The food was a little pricey but good. The drinks averaged about $6 for mixed and were good. The Pizza was about 14" and tasty. Probably the best bet to feed a larger group.
When a large airplane comes over the beach, it is something else. Also interesting but not really recommended is standing behind a large jet as it takes off. The wind is pretty awesome but as the sand starts hitting you, that is no fun! As I mentioned, the beach has a tendency to erode and can be different sizes at any time or completely gone altogether. It was pretty small when we were there but accommodated all the people fine. There is a unique phenomenon when the beach is smaller in that a wave will come ashore and then sometimes fall back in a manner which will create a wave going away from the beach. It's kind odd the first time you get hit in the back with a wave coming from the shore.
St Martin is a very nice and safe island. Somewhat similar to Grand Cayman, you can tell that there is more money here than most places in the Caribbean. We didn't go anywhere near the entire island but we did see a lot and overall, it is in much better condition than St Thomas. There are some all inclusive resorts here and if airfare wasn't so darn much to travel to the Caribbean, I would love to come to St Martin for a few days on vacation.