DS is not a tween yet, but DD is nearly a tween (9.5 years old). From her friends, I can say that Legos and Minecraft are big hits. Sports are also big.
Food is always good, especially with teenage boys, I imagine. Things like chips, candy, cookies, gum, or other snack foods.
Stickers might be good too, bigger stickers like bumper stickers, with pirates, Nightmare Before Christmas, or Disney quotes from Pirates or other "boy" Disney movies. Or smaller stickers to decorate notebooks, phones, iPads, etc.
Notebook/pen, sketch pad/colored pencils, notepad, cool customized pens (with cruise dates, disney quotes, etc.), really any "cool" office supplies would be good.
If you are really crafty, how about a treasure hunt? Make a list of things for them to find, themed to Disney movies.
A baseball, tennis balls, golf balls, ping pong balls, etc., maybe decorated with something Disney? My brother is nearly 40 and he always wants to bring a ball to play with DS because you can always find/make up a game with a ball.
Sweatbands/wristbands (those terry cloth ones you wear while working out), or a small towel for wiping off after a workout/practice.
Water bottle!!!! Can't have too many of those!!! Good for any age!!
Deck of cards.
Baseball cards.
Those waterproof cases that hold credit cards/money/small phone.
Wallet.
Small boxes or containers. DS really likes hiding things in containers. Gonna make for some rough teenage years.
