I don't do a ton with younger kids but I do start once they show an interest and can sit with me and follow direction. My 18 mos old colours, does stickers and paints but she is also a second child so she does a lot of things earlier then most. What about art that they can eat e.g. paint with pudding, homemade finger paint (food based) or one idea I've heard on here but haven't tried is a piece of paper in a freezer bag with some squirts of paint inside that they can mush around on top, take the paper out and voila. Clean and they can't eat it.