I think that the flash drive is a great idea. I know they have some 4 gb at Office Depot right now for $12.99 that have all kinds of fun designs on them.

As far as candy and treats, have you though about doing Personalized Fortune Cookies? With it being a martial art theme, I thought that could be cool. You can make the fortunes read whatever you like or just thank them for coming to the party.

Just a thought!