I've been on 10+ cruises, this is my 2nd on Liberty of the Seas. My wife and I are in my 50's and my BIL joined us (early 60's). Here are a few notes that hopefully will help you navigate post-pandemic cruising. Cruise had just over 3K passengers, which I think was about 75% full.
Original cruise was going to Jamaica and Grand Cayman, but Grand Cayman is closed because of Covid - so we did Belize and Roatan instead. Been on the Belize/Roatan/Cozumel itinerary many times, so it was a bit disappointing (although we do love Belize).
Covid - You need to get a test 2 days before you board. Not a big deal, free at CVS and got the results within an hour.
We started with a guaranteed outside room. Got unlucky and got deck 2. It was a tiny room and a long way from everything. We went to the pursers office and were fortunate enough to get a room on a higher deck that was actually a spacious ocean view for the same price. Trust me, the extra 20 square feet makes a big difference.
Steward was great, but on all of my cruises with each line I've never had a complaint.
Our second time going tubing. We used Cave Tubing R us with David Almendarez this time as well.
SUCH a good excursion... It was half the price of the excursion on the boat and the 3 of us got a 'private' tour. Make sure you get the lunch as well - his wife is an amazing cook, made the Belizean national dish of Stewed Chicken, Red Beans/Rice and Potato Salad. The best meal I had all week.
The best part about Belize is the people. Everyone is friendly and relaxed and you aren't accosted when you leave the port like you do in other ports. I can't speak highly enough about the country and the people.
Be sure to try the national beer, Beliken. I suggest the Beliken Stout. David stopped for us on the way so we could get a 6 pack at a local store.