My granddaughter just got home from Disney World (U.S.A.). I didn't go with her this time - but she had a wonderful time!
My husband and I took her to DW 3 years ago and you are exactly right - the look on the face is PRICELESS!!!!!
She was 6 at the time and I said that maybe she was too young because she wouldn't remember it. My husband said, "Yes, she's young, but if we wait, she won't want to ride and do everything with me." I realized right then and there, that the trip was as much for him as it was for her. He rode every ride with her, Dumbo, It's a Small World, Peter Pan - every single one and I wouldn't trade those memories for anything in the world!