From the Grad Night site:
Acceptable Attire for Disney Grad Nite
Dress to Impress: What's in and what's out for Disney Grad Nite Apparel.
Boys
Casual pants (including khaki style and jeans), shirts with collar (golf style shirts, dress shirts), sport jackets, dress suits, comfortable shoes (including tennis shoes, dress shoes, and boots). Girls
Dresses, skirts, shorts, casual pants (including jeans), blouses and tops, and comfortable shoes (including tennis shoes, dress sandals, and boots).
We've got your back, and to make sure things run smoothly, we'll be searching everyone and their belongings before entering the Park, So, here are the things that need to be left at home:
Any clothing affiliated with a school, professional sports team, group, club, etc.
Clothing not in good repair (torn jeans, pants, shirts, etc. ) Jeans are okay as long as they are not ripped or torn.
Revealing clothing (i.e. bathing suit tops or bottoms, cropped tops, see-through clothing, etc..)
Hats and/or Bandanas (Either worn or hanging from belt loops/pockets, etc..)
All backpacks (Small purses or hip bags are okay).
Weapons, knives, laser pointers or chemical irritants are not permitted.
Students or chaperones not following this guideline will be dealt with at the discretion of the Orange County Sheriff's Office.
Alcohol and tobacco products are not allowed and will be confiscated and not returned if found on site.
Please note: Failure to follow the guidelines may result in delayed admission and /or denial of admission to your Disney Grad Nite event. Also, Walt Disney World Cast Members have the right to refuse admission to anyone they deem not appropriately dressed for the event and not following these guidelines. The dress code for Disney Grad Nite will be enforced throughout the event by all Cast Members working the event.

My kids are 14 and 17. They both own clothing from Texas A&M, KU, North Carolina, Kansas City Chiefs, and their own high school that they wear frequently. Do you think this will be a problem?