Cookies and rice krispie treats made on sticks like lollypops. Dip some in chocolate (not all the way, maybe just half) and sprinkles-- these are a big hit with the kids.
Cookie alternatives, like chex mix or fudge, and brownies. I would stay away from cupcakes.
Items that are peanut free and labeled as such (and kept away from the other items.
Sugar cookies in seasonal shapes, some plain, some with pretty frosting or sprinkles, some with candies.
I agree some shortbreads, maybe the ones with some jelly in the middle (thumbprints)--depending on your target audience, "mature" people love these!