At the entrance to each park you can get complimentary 1st Visit buttons to wear during the trip. You can also get one if you're celebrating an anniversary or birthday. Wearing the buttons can also get the kids a little extra attention from CMs or even from the characters. My DD wore one on her 1st visit and was over the moon when Cinderella commented on it and spent extra time talking to her because of it. DD still talks about that, even though she was only 3 and she's 7 now. She remembers it so clearly.
I second the caution about setting the bar too high. If you plan on going back in the future, try not to overdo things. Save some of the extras for future trips! And since kids have no idea how many things you're able to do at WDW, they're happy and satisfied as long as they get to see their favorite character or favorite ride. Each year we go I ask DD7 and DS4 what are the top 3 things they each want to do. Our trips are then planned around what makes the top 3 for each child. It helps a lot with planning and it prevents us (parents) from overdoing it because we want to make the trip a great experience. For instance, for our trip in Sept. I was going to make ADR at 1900 Park Fare for a dinner with Cinderella, DD's favorite. When I told her, she said she's already seen Cinderella so she'd rather go to the restaurant with unlimited ice cream (Trail's End at FW). As parents we want to do everything for them, but the kids don't usually want as much as we want for them. They're happy with the simplest things. It's so hard to remember that, but it's true.