Disney is absolutely phenomenal for families and kids! We've been on 2, and are going to doing a third, and my daughter has a blast! They really cater to the kids plus they have the characters like Mickey, Minnie, the princesses, etc. on board. Just FYI though - kids have to be at least 3 years old and potty trained to be able to drop them off to the Kids' Club; kids also have to be potty trained to go swimming in the pools - no swim diapers allowed. Just something to consider if you were thinking of waiting until your younger child is 3 or 4. The Kids' Club is a ton of fun, and if you let your 6 year old daughter go, she'll have a great time and probably even make some new friends - it's your decision, but there's no reason to have them attached to your hip the whole time. While DD is having fun in the Kids' Club, I am able to work out, lounge by the the pool, etc. It's very safe and secure too - they don't let any child leave without a parent and parents have to show ID and give a secret password to pick them up, so I've never worried about anything bad happening. We also get ship phones that they will call in case we need to come get here for some reason.
http://disneycruise.disney.go.com/ships-activities/ships/...
http://disneycruise.disney.go.com/ships-activities/ships/...