How old are your granddaughters? If they go to school, then try to go on a weekday when they have a day off. Don't even TRY to go on a weekend, It will be disasterous! And don't go on a national holiday, either. Just try to go if they have parent confrences or something.

Sorry, I don't have anything to say about where to stay, even with all of my disneyland experience. hehe! Have you tried going on to their website yet and looking at the hotels?