I absolutely second-motion the wine idea! Let him dribble it over you and lick it up .... mmmmm!
Chocolate syrup, whipped cream, etc all very good ideas but make sure you lay something (an old blanket or whatever) on the floor to save the cleaning bills!
Personally I want to try some edible finger paints....hmmmm!!!!!! Have some fun diddling on some human canvas and more fun cleaning it up!