Charli, can you find other cheerio type cereal at a health store? There are other brands here that are healthier than things like Cheerios. Natures Path makes corn, millet, and rice puffs that have nothing offensive in them. They also make their own 'O' cereal that is healthier than regular cheerios. Maybe if you have a look around you'll be able to find something.
Cheerios pretty much turn to mush when wet, like pp mentioned, so not much of a choking hazard.