Hello Kyle!
Welcome to planDisney! Filling out forms online can be such a tedious affair and I have made the same mistake as you and entered the wrong information sometimes. Swiping too quickly or letting the device "auto-fill" fields can sometimes sabotage all of our best efforts.
When creating your
MyDisney account there was a point where your birthday was supposed to be entered and it was very important as it determined eligibility for certain experiences and ticket options for the Parks. If you wish to have that changed, it will mean a phone call with a friendly Cast Member at
Technical and Website Support. Now, if you are trying to change the date of someone you are managing then you can change their date via the
Family & Friends List. Click on "Settings" next to their name and edit in the newly opened fields. Don't forget to hit "Save!"
Make sure that you fix all of these birthdays before you
purchase tickets and make dining reservations. While we may be kids at heart those 10 years old and older are considered adults in the eyes of Disney. Prices for everything are affected. I did recently learn on my last trip that even though my son was 10 he could still order off the kid's menu which had better food options for his picky palate. It never hurts to ask your waiter when dining as chicken tenders are delicious at any age.
I hope this helps and you have a lovely time if you visit the Parks!
Happy Planning!
-Nimmy