It's always a good idea to have a few super simple crafty ideas that can be set up in seconds and aren't overly complicated for under 5s. Here's a cooking cheat that involves no actual baking but all the fun of decoration.
It's also a fun activity if you have a larger group of kids to keep occupied as it doesn't require lots of one on one supervision.
Time: 10 minutes (more or less time depending in attention span)
Age: Under 5's
Flat, plain cookies. If you're in the UK then something like a rich tea or digestive is ideal.
Lay out your cookies, a bowl of icing with a teaspoon and a jar of sprinkles.
Kids can now spoon icing sugar onto their cookies.
Spread the icing sugar over the cookies and then shake those sprinkles to your heart's content.
My son really enjoyed making these at a Christmas party that we went too. I noticed that the older kids were really engaged too. They used larger sprinkle balls and little sugar hearts to make more interesting designs.