We've taken our kids and grands twice on Carnival. Two years ago, the kids were too young to enjoy Camp Ocean. This year, the 5, 4 and 3 year old kiddos actually begged to go. Our 18 month old was too young for the program. The kiddos also spent a lot of time at the waterworks area. We chose our excursions with them in mind. Ocean world in Amber Cove was a big hit. We did the MDR once on our first cruise. The waiters were awesome with the kids. This year, we did the Lido buffet every night. It was too much to expect for them to sit through a long service when they had had long and busy days. Divein movies by the Lido pool were a big hit. They ran Moana the last night and that was a great way to end the cruise.
The key to taking young kids on a cruise is to not put them in situations they aren't mature enough to handle. Somebody has to be watching them at all times, no exceptions. We had a great cruise and I didn't see any eyerolls from fellow passengers, so hopefully they didn't disturb anyone.