Forgive me if I have this wrong, but I don't really think that cruises are right for your family at this time, OP.
The reason I am saying this is that most people when they investigate their first cruise are full of optimism, and ask the doubting questions once they have thought about it. You seem to be full of doubt from the get go, right down to the towel art, lol.
Last year, I thought about going on a river cruise, as lots of my friends have done these quite happily. I thought it would be great to be in sight of land (5g!), walk off into town centres, have basic excursions included, flight from Heathrow, etc. Then I start on the negatives - expensive, being strapped to other boats during the night, very little outside of German speaking places,etc. The itinerary is the most important thing to me, and I haven't found the right river cruise yet.
I've looked up some of the suggestions here for higher end cruise ships, and really, I wouldn't feel comfortable taking the risk. I don't need 6* food, and everything we've experienced so far has been more than good enough for us. I want my ship to look like a ship. I don't need ice rinks, etc., nor would I want to go on an American dominated ships. Mumsnet loves the faux brags, so take with a pinch of salt.
There is an undertone here about the class of fellow passengers and I just have no time for that.