Every guest brings a different cheerio-based treat. Some examples might be rice krispie treats with cheerios instead of rice krispies, or a chex-mix style party mix with cheerios instead of chex mix. Or even just cheerios with milk and bananas. The sky is the limit when it comes to elaborating a cheerio-based dish, really.
For party activities, you can do some crafts using cheerios, such as making garlands or pasting them onto construction paper to make pictures. You can make a cheerio necklace, too.
For more ideas, or for a neat prize at the cheerio party, you could also consult this book.
There is also a card game called cheerio. It would therefore be appropriate to play at the cheerio themed party. You could also play bingo with cheerios for markers.
Also, anything surprising involving these cheerios would be a funny pun.
