The TS characters in the parks...can they sign? I was thinking a fun thing to use for autographs would be the free TS clock from the TRU TS3 deal....but, obviously, if they can't sign, it won't work!
The Green Army Guys can also sign at times (we were lucky enough to get to go through the line to see Buzz & Woody in DHS with them at a slow time when TSM was closed for refub; SO much fun).
Buzz is a stamp, but you can also speak with the attendant about getting it signed by all of them.
Let your kids get the pictures and hugs and such. And then speak to the attendant to see if they can hang onto it for a bit, and you go back in about a 1/2 hr to an hour later and get it. It's been done before.