We had an 8 month old, 2.9 year old and 4 year old during our 2/26/05
Disney cruise.
We went to Cozumel to Paradise beach. I was a bit nervous about this for several reasons.
Most importantly I had the car seat stroller, so it converted to a stroller with wheels, or the wheels flipped in and could be used as a car seat. I bought this specifically for this trip. I was terrified of having my children drive in a taxi, or bus in Mexico (or anywhere) without carseats. My 2.9 and 4 year old I was OK with putting in a seatbelt, I didn't feel great about it, but it was OK.
My baby needed to be put in the carseat, and on our first trip, we had too many people with us, and he had to sit on my lap. I was furious and scared.
On the way back, we got our own taxi and I kept him in his seat the whole time, and I felt way better about it.
The other problem I found was with taking a stoller, you need to either go up and down in an elevator, or you need to fold it up and use an escalator, to get back and forth across busy streets to and from the cruise ship terminal.
You will go through a busy shopping center, and that was fun for the kids.
All in all, it was ok, I do think that if I had to do it over, I would of stayed on the boat, or strolled around right off the boat where the shops were. It was alot of work for a short amount of time at the beach, (which was beautiful), but not for little, little babies. It was hard to keep him in the shade (they had beautiful umbrellas) but the baby was way to busy for that.