I would say it depends on your child. I have seven children and I would go w/a 9 mth old. I love that age!

We were thinking of going this fall w/a 9/10 mth old. My husband wasn't too sure, but he doesn't have a good memory for that young. He just thinks a lot of work.(we decided next year because we are spending $$ on the house and the three youngest will be 1 1/2, 4 and 5 which I think will be perfect ages! One of my favorite ages at disney is 1 1/2! Their expressions are memorable!

We have gone w/ two others at that age and my husband does remember that age and the expressions!!!

I have gone all sorts of places w/9/10 mth old babies. I have brought them to conferances and sat them on my lap for a whole weekend. They've been great! Course everyone else was surprised and commended me. But you wont be just sitting. Your child should be quite amused.

An older sibling to be amused w/will help also! I personall would have nap/rest time in the mid day. It will be at the hottest time too which will cut out on worring about burning and the hottest heat for cranky babies. If your 4 year old doesn't take naps one of you can enjoy the pool w/her! Thats what we did and it made all the differance!
I am big on naps and rest times. I am going out on a limb, but personally I think it makes the differance between a very happy child most of the day and a fussy , bratty child. Whenever our children start getting unruly or fighting it is almost always because they are tired.

(lets face it, when we are tired our patience is thinner and our emotions are harder to keep under control) We then talk to the older ones that will understand about learning to control your actions even when you are tired. Sorry to get on a soap box, just my two cents.
