We gave Nathan playdough today, and he tried to eat it over and over. But if Finn isn't as oral, it should be fine! And hey, it is non-toxic, right?
Michael's (the craft store) has these foam shapes with sticker stuff on the back. Nathan loves playing with those, although they stick to his hands/clothes/face as often as the paper. And you can get ones that require glue instead. Crayola also makes a line of colouring supplies for toddlers 18 months +; I think that they are called "Scribblers". They are little paint brushes that fit in the palm of a child's hand, and the paint is inside so there is no dripping. Well, that is the idea anway. Nathan did try to suck on them, but he also anjoyed painting with them. Scott has lots of "art" around his desk at work already!
There is also things like chocolate pudding as finger paints, that is messy but really fun.