Whenever we've gone, the cast members often have stickers that they are handing out to kids. I'd bet if you talk to a sympathetic CM, they'd give you 22 stickers to take home to your "kids". We often got them in the shops when we were purchasing something - the CMs have them behind the counter.
It can't hurt to ask.....even if you ask for 2 or 3 at a time and accumulate them throughout your trip.
Also, you could pick up 22 park maps and use them in a lesson plan when you get back, such as map reading or something, or just to tell the kids about what you saw when you were there.
Postcards are often inexpensive and make great souvenirs!
Also, I've told cast members how I like to use the small bags (that they put purchases like post cards in) for the rest of the year until I can come back to Disney World, and several have given me extra small bags for free. I figure it's free advertising for them because I've become known as the Disney Lady at work and I help everyone else plan their trips.
I'm sure I'll think of more ideas as soon as I post this...LOL.
Best wishes for a great trip!
Doreen in PA