Yes those will work. They are used to all kinds of writing instruments! We got the plush kind (Mickey Mouse) at the Disney store and they seemed to work really well since they weren't slippery and are fatter than a regular pen.
I took the "fat pens" last year and alot of the characters preferred regular pens. I also had a fat sharpie and they really marked up their costumes (permanent ink) so this year we just used a regular pen or a Disney Pen that we bought in the gift shop.