I would never try to buy a child's pass for a child over age, but my 8 y/o is already 5'1". When we go back to WDW, he will still be only 8, and at the rate he is growing I'm sure he will be 2-3 inches taller. Should I take a copy of his birth certificate, or do you think it will be a problem? We will be buying AP's as we are moving to Florida in Dec. He won't turn 9 untill the end of March. Any suggestions would be great, as my 7 y/o is only 2" shorter than his brother.