I cruise quite a bit. It's relaxing.
I dove Coz while cruising with Royal Caribbeans (2019). I used their Shore Excursions and the prices were reasonable for a two tank dive. All dives from the Shore Excursions are in the morning, no afternoon dives. Logistically, it's not possible for cruise dive ops to get in a 2 tank dive and get you back in time. Our boat had 8-10 divers plus one check out diver w/ the ship's DM - we split in 2 groups plus the new diver. Very organized. The Dive Op had their tender at the dock ready to take us to the rental shop and equip us.
The current in Coz, when I was there in August, was crazy fast. I lost my dive buddy TWICE on the same dive - he was too busy futzing around with taking pics and lost our group ONCE because of him (found them again within minutes). Stay with the group as much as possible. BRING YOUR SMB and reel, just in case you get separated from your group. There will be lots of dive ops/boats hitting the same dive spot. Remember your boat's name. If you get separated and can't locate your dive group within minutes, hook up with another group and when you surface, have that Captain radio to your boat. DO NOT SURFACE ALONE unless it's an emergency. You will not see your DM, your boat, or any other boats nearby. The boats track the dive group and will be at a rendezvous point.
Sign your family up with a Shore Excursion weeks before departure, they'l get a discount. Eat breakfast early onboard the ship or have them do room service. The ship disembarks from Forward and Aft of the ship. You'll be done with your dive by noon or 1pm. Plenty of time to reconnect with your family to do some shopping or nearby sightseeing.