Hi Gabriel!
Let me be the first to wish you a very Happy Birthday! I know your Walt Disney World Resort vacation will be even more magical because you'll be spending it with your family on your special day.
While there's no way to sign up for the honor of being the Grand Marshal of the Magic Kingdom Park parade, I've read several online trip reports from guests who have had the honor bestowed upon them. I've always wondered what the secret is to being chosen!
From the trip reports I've read, Cast Members randomly approached the guests in the park, struck up a conversation, and asked if they would like to be the Grand Marshals of the parade. (How could anyone ever say no?) The guests are then given instructions on where and when to meet up before the parade. They're asked to provide their names and hometown information (to be announced over the sound system - how exciting!), and then they're free to enjoy their day until parade time. There's no secret formula to get chosen to participate in the afternoon parade, but I've certainly got my fingers crossed that someday it might happen to us! Currently, the afternoon parade is the
Disney Festival of Fantasy Parade, and it's AWESOME. The costumes are so colorful, and the parade floats are phenomenal. The steampunk-inspired Maleficent dragon is my favorite!
To find trip reports of families who have had this amazing experience, you can search the internet for "WDW Family of the Day". It's so much fun to read about families getting chosen for this awesome honor!
Make sure to pick up a birthday button at your resort hotel or stop by Guest Relations to get one - when you're wearing your button, Cast Members will do their best to make your birthday extra special!
Thanks for stopping by the Disney Parks Moms Panel with your question! - Diane W.