I think the cruise will do wonders for you. There’s nothing fun or normal about a life centered around knees. You’re still early enough in your recovery to want to make some accommodations — no long hiking shore excursions for you — but cruises are good for being able to pace yourself. If you let your cabin steward know you will want the ice bucket kept well-stocked, you can make your own ice packs with some zip-lock baggies (quart or gallon, test drive for what you like best). I found ice packs very helpful post-exercising/walks until I was about six months post-op.
The sleeping sorts itself out. Sadly, it does not do quickly enough for anyone. I had less than optimal sleep for about four months, and I was off narcotics at three weeks. It’s so many things, including that the knees act up in some positions, and that we can’t turn over normally at first, or sleep in preferred postures, and that our bodies and brains are re-calibrating all kinds of massive changes that happened because of our surgery. It can feel at times that we’re permanently messed up. We’re not. It just... takes time. I’m back to sleeping normally, including my superpower of being able to drop off to sleep in two minutes flat. (That took over a year to get back.). Hang in there!