1) I prefer late seating. We're always late whenever we have early seating (usually because we're fighting over the hair dryer or shower or something). And we would miss pictures. I say definitely go late. Sometimes they have special show viewings for late dinner guests. And this way, you know you're hungry for dinner, and you're probably less likely to overeat at midnight buffets.
2) We usually do one excursion per port of call. St. Maarten is definitely the prettiest of the two islands. I suggest morning shopping time. And beware of beaches on the French side. You might be in for a surprise.
I hate St. Thomas. So I'm a little biased I suppose. But I do not recommend dolphin encounter. If you want to interact with dolphins, I suggest Discovery Cove. This is like the dolphin exhibit at Sea World. You sit around a pool with dolphins and they bring the dolphins up to you and you can pet them. And only one family can get in the water at a time. You aren't really swimming. They just bring them to you in like four feet depth. It's a disappointment. And in case you're considering snuba, I don't recommend that, either. Especially if "Cocoa Beach" is mentioned. Do not go there. We did snuba and they gave us one air tank for the five of us. We ran out in ten minutes. It was a rip-off.
3) You can book in advance online... or you can wait until you're on the ship. Actually, that's usually how we do it in the Caribbean. I know on RCI you can book using your TV.
4) Now, I'm not the one doing the money and stuff, but I read a lot of Conde Nast and Travel and Leisure, and neither recommends airfare and cruise line packages. However, if you do book them seperately, if something goes wrong with the flight, you're not guaranteed on the ship. (However, if for some reason you miss the boat, you can fly out via helicopter and catch up.)
5) Obviously I've never had a romance package.
But it sounds delightful... go for it!!!
6) We have stayed in an inside stateroom once, and it really wasn't that bad. We typically don't spend that much time in our stateroom. It did feel a tad bit like a closet at first, but I got used to it. There is a fake window with a light, so it doesn't feel like you're trapped inside... just that your shade is permantly closed. Kind of an evening feel. But if you aren't going to be spending much time in your stateroom, an inside one will definitely work. And personally, I don't think there is much use for a verandah in the caribbean. All you see is blue... blue... and blue. But I don't find it depressing. No.
Well, hope you have a fabulous time on your cruise!