This great marshmellow fondant recipe is a sure winner...and incredibly easy, too! All you need is marshmellows, powdered sugar, food coloring (I like the gels) and a touch of water.
The following site has you knead this play-doh-like icing with crisco hands, but it is even easier in a heavy mixer. Just grease the bowl instead of your hands. It is very quick and a premade batch of primaries are a great mixing activities for your little guys. They love this treat!