Wendy - When one of my kids was in kindergarten, they marked the 100th day by making necklaces from Froot Loops and Cheerios. They used yarn, and the kids counted the cereal rings out themselves (in groups of 10, easier to keep track). Some of the kids wanted to eat theirs right away, some took them home for a sibling or parent. Buy the store brand cereals if you want, and be sure to figure in enough so that there's plenty for little hands to sneak snacks! Take your camera, and snap a photo of everybody wearing the colorful necklaces.

Or maybe make a sheet cake, and top it with 100 chocolate chips or M&M's. I'm having a hard time thinking of anything that I'd want my kid to eat 100 of at a time, other than maybe jimmies, and as you pointed out, that's way too much work for a 2K mom! June Cleaver maybe, but not us!

Good luck - let us know what you decide to do, and how it turns out.