Hi,
Our DD was 3 and our DS was 11 weeks old on their first trips.
Every child is different, and unfortunately, you can't possibly know how they will react to a 9 hour flight, without actually doing it!
Our DD has never been any trouble, but our DS was a completely different kettle of fish! A little s*d pot when he was little, especially when he got tired!! But, saying all that, he has never been a problem on our flights over the Atlantic. I always made sure I'd got plenty of 'back up' toys and games that were new to him, just in case!!
One of the beauties of taking your kids from a young age, is seeing them 'grow up' with Disney. Every year, they will have a new 'favourite' ride. And seeing their faces when they meet their favourite Disney Characters for the first time, is absolutely priceless!
Tracy