My opinion would be the 2 year old would be a little too young for it. I'm sure they would enjoy it but I don't think they would "get it" as much as an older child. If there are older siblings along, then sure go ahead and bring the 2 year old. However, if that's your only child, I would wait until a bit older. That's just my opinion though. We went in the middle of summer and had a couple stroller kids with us -- it was hard getting through the crowds for those parents, the tourguide did a great job making sure none of us got seperated or anything, I just felt sorry for them.
I sent DH & the 1 year old back to the hotel while the 3 older kids (11, 8 & 5 at the time) went. We all had a BLAST. We will definitely be doing this one again.
Remember your autograph book & camera.