Great idea....I love it!
For small holes, different sized piping tips work perfectly.
I would use fondant & tylose myself, or better yet, because it's a cupcake topper and might be eaten...I would try modeling chocolate.
I don't work with gumpaste, so I can't comment on that.
(I know you didn't ask, but I have another tip that might help...if you're planning to "dirty" up the mask and don't have brown petal dust, you can use cocoa powder and a brush...it works...