My magical moment was on my daughter's first trip to WDW. She was 2.5.
As with many other little girls, she is a huge Cinderella fan. We have all of the movies at home. She acted them out, etc.
When we walked into MK, went under the train station, and made our way to the center of Main St., and saw Cinderella's castle for the first time, she was in disbelief. I'm videoing the whole thing and my wife and I were welling up (I'm starting to now as I think of it). My daughter just smiles and looks and couldn't say anything.
Her look was, "I can't believe that Cinderella's castle is real?"
I'll never forget that day as long as I live. It was that day that I brought my first child to MK and I could see the happiness in her as it was for me as a child. It was at that point that I knew that I now travel to WDW for my children's enjoyment. My own, is secondary. Everything that happens there. Every smile, every laugh, every memory, is for their enjoyment.