My kids really enjoyed doing the pressed pennies. It costs 51 cent each and they have them at most gift shops. You can also buy a book to put them in for around $6.
We also get a souviner popcorn bucket every trip.
Last trip I got my DD(3) a small pirate Mickey set with Pirates Mickey, Donald, and Goofy and boat for around $6 at the POT gift shop.
My oldest always wants a stuffed animal.
My son likes the Disney match box cars.
They also like the Mickey shaped pens and pencils and they have Pooh, Tigger, Pluto shaped ones and lost more.