well my son is 3 and i have been "pumping" him up about moving for a week or so, and we're moving in a little over a month lol. i just tell him, not today, but in a little while. and he helps me "pick out" houses while we're driving lol. it's a little different because we're not moving far away from friends and family, but i'm trying to get him used to the idea and that it's nothing to worry about, tell him how much fun it will be, how he's going to have a brand-new room to play in, and how we're going to put aaaalllll our things in boxes (name them off, toys, books, clothes, etc) and take them to the new house. i'm mostly worried about sleeping in the new room. he definitely needs a heads up. but other than that it just depends on your child, and i'm not sure there's a way to know how best to do it until you've been through it. maybe someone on here will give us both some better advice!