Hello, Staci,
I absolutely love your idea of having characters sign a large Vinylmation! If you don't mind, I may have to copy your idea and do the same thing. I'm silly crazy for those little Mouse figures.
The characters can sign nearly anything as long as it isn't being worn, so you should be okay. However, please note that policies do sometimes change. I'd also keep in mind that a few characters may have difficulty holding the Vinyl in order to sign it and may need some assistance, but they won't be able to tell you directly.
I also did a quick internet image search for
Vinylmation with Autographs and found many images of other guests who did the same thing; it is fun to see how all them turned out.
Finally, if you happen to be a Vinylmation collector, did you happen to see the recent article on the future of them at the
Disney Parks Blog? I personally stick with the Vinylmations, but I have to admit seeing the Orange Bird Park Starz in the background of one of the photos has me tempted to branch out my collection!
Have a magical trip; please let us know if we can help again.