I've done a few: Alaska when I was a kid (Paquet), New England (Princess), trans-Atlantic (Cunard), and a small private charter (16-berth) in the Adriatic. I can't speak to the specifics of your situation, but I'll just relate my experiences in the event they might be of use somehow.
I don't remember much detail about the Alaska cruise, but I have positive memories of the excursions (helicopter to a glacier, floatplane to a lodge on a river) and of being allowed to shoot skeet off the stern (I was probably about 14).
Of the big ships, Cunard was at least an order of magnitude better in every way than Princess. The New England cruise worked largely because we stopped every day and spent a lot of time off the ship and away from the crowds. We never did the excursions, just got off and started walking. It was, however, entertaining in a perverse sort of way to watch the ever-increasing displays of gluttony - we saw a couple polish off a good 40 lobster tails in a sitting. But it was basically a big sea bus filled with people determined to eat and drink themselves silly for a week, and do it loudly.
Cunard was so much nicer it's almost a completely different discussion. The ship was about the same size as the Princess vessel, but it carried fewer than half the number of passengers (maybe around a third, IIRC). Lots more space, much more relaxed attitude among passengers and crew, and overall a much better experience. We wondered about going a little stir-crazy being at sea for seven days, but it was incredibly relaxing.
The small boat was again a whole different experience. I went with family, and I did not make the guest list. On the plus side, great opportunities to visit out-of-the-way places, swim anywhere you want, much more visceral experience. However, you do need to make sure you like your traveling companions, as there is no space. Even with cabins with private baths, space is at a premium, voices carry, and there's really nowhere to go if you need some time alone.
The small boat was the only one I used the internet on. It was satellite but pretty decent. Cunard had it but charged some obscene sum for access, and I preferred to be disconnected. I never even checked on Princess, as we just used public wifi on shore as necessary.
I can't imagine trying to enjoy a cruise if you a prone to seasickness. It just seems like a struggle - not exactly what I look for in a vacation.
Of them all, I would do the Cunard Atlantic crossing again in a heartbeat. I would do the Adriatic again, but with more control over who my shipmates would be. I'd like to see Alaska as an adult, but finding the right ship is key. The river cruises mentioned in this thread intrigue me - they seem like a good combination of things I like about cruising.