Hi,
@mikewdw
If your ports are St. Martin (our favorite, btw) & St. Thomas you'll be on an Eastern itinerary. Westerns go to Cozumel, Grand Cayman, etc.
Just so you don't get confused.
1. If you go on an excursion thru the cruise line they'll provide you towels. If you're going it alone you can go up to the pool deck and get some towels to take with you off the ship. Just be sure to kindly bring them back.
2. Pre-packaged snacks typically are upcharge items on the ships. I think I *may* have seen the little baggies of chips at one of the walk-up burger/sandwich windows but I could be mistaken. I asked my hubby & youngest son. Hubby says he thinks he may have seen them. Son says he doesn't think so. Don't take our word for it. One thing you CAN do is pack a bunch of empty ziplock baggies in your luggage. I always bring a quantity because they're always handy. (put cameras/phones in at the beach, etc.) Anywhoo, get some cookies and put 'em in baggies. There's a little something you can have. If you're worried about having munchie stuff in ports you can pack yourself some pre-packaged stuff like jerky, granola bars, m&m's, etc. in your luggage. You *can* bring food onboard with you as long as it's commercially packaged & non-perishable.
3. We typically carryon our electronics, my jewelry (or any other valuables), bottles of liquor, medications, my cosmetics/toiletries, and anything else we might not have fit into our checked luggage. The pools/slides aren't something we usually do on embarkation day but if your family will want to do that, then your idea to bring swimsuits is correct. Don't forget the sunblock!
4. Nope. Sorry, steamers are a prohibited item. If it's found it'll be taken. My mother-in-law recently was reading some traveling light article and came across a great suggestion. Flat irons (like for ladies hair) aren't prohibited. If nobody in your travel party already has one or if theirs looks as well-loved as mine, pick up an inexpensive one and you can touch up creases with that. I thought that was a creative idea. There's irons free to use in the laundry rooms onboard and you can have your clothing pressed via the laundry/dry cleaning service onboard. We usually pay to have everything pressed. It's not crazy expensive.
5. Try to bring the least amount of anything that you can get by with, shoes included. My hubby & sons usually bring a pair of sneakers, a pair of flip flops, and a pair of dress shoes. That covers everything they need. I live in flip flops. Sometimes I bring sneakers. Then, of course, I have to bring sandals and heels to match my dinner attire selections.
6. If you are on an excursion with the cruise line and the forecast looks like rain is likely they often give out ponchos that look just like the ones sold in the parks. They give them for free! Even if you aren't on an excursion and are just leaving the ship, if rain is threatening they'll often have a CM at the gangway handing them out to anyone who wants them. I have a set of 4 that I collected in my travel junk box that have never been used. I bring them on every vacation juuuust in case. You can also get the little cheapy ones at Walmart or Academy and bring those with you. They're nice to have just in case the ship isn't handing them out.
7. It depends on what time you board and what you want to do. Most everyone boards and goes to lunch. We board, go to guest services (to make Mixology & tasting reservations, get an extra Wave phone, etc.), then go find lunch. At first they'll tell everyone lunch is being served in the buffet venue. Usually around noon or so they will open one of the sit-down venues with a smaller version of the buffet & beverage service. After lunch but before staterooms are open we'll go wander around the kids clubs during the open house because that's our chance to go "play". My "kids" are 16 & 18 but we're all still big kids. The kids clubs are sooooo neat with such awesome theming. It's just fun to go play around! Do whatever you like, tho. Some people go straight up to the pools, stake out their spot, then go fetch grub to bring back out to the pool deck. We just aren't that into the pools.
When you get to port and check-in there will be some CMs about handing out the daily Navigator. That's the schedule of everything going on for the day. There's also great info as far as what's open, hours, etc. Definitely get one and look it over.