I agree with everyone that said it really depends on the child(ren). If they're not Disney vets, DL can be kind of big and scary for a young first-timer.
My oldest DS was 4.5 when we took him to DL for the first time. He was one of those who sometimes would get very overwhelmed in a new situation, so the night before (while staying at Grandma's in OC) we showed him the Sing-Along video about Mickey Mouse at
Disneyland (we've had it since he was a baby, so it's got to be at least 12-13 years old now). We told him that was what we were going to be doing the next day and let him ask questions. He had a great time.
Three years later, similar set-up, we were taking DS (7.5) again, along with DD (4.5). She is much more easygoing, so we told her we were going to see some family friends that morning (we told DS while we were getting ready and warned him to keep it a secret -- he was so proud of himself). She didn't have a clue until we pulled into the parking garage. Also had a great time.
I suppose if I were coming from a long way away, I might keep it a secret until a month before and then use a countdown chain (my kids love making them). Maybe tell them about the trip but not about some of the details?
I have a hard time keeping secrets from my kids, especially since they can read (over my shoulder sometimes) and I do so much online research for our trips. I am super-advance-planning a family Alaskan cruise for 2010 and have no idea how long I will be able to keep that under wraps.
PHXscuba
"You can't have everything -- besides, where would you put it all?"
