harry potter, would i be found out if i swap a kids ticket for child?

[SunnySummerDays]

I have a family ticket , but 15 year old doesn't want to go. Do you think if I substitute him for a petite 20 year old girl they would suss it out?

I have a code to swap for a ticket when I get there.

Thanks

Nah... ask her to dumb down her make up and wear her hair in plaits. You'll be fine.

Do I just queue up with my paper ticket to swap for a real ticket...I just have a printed code.