The tactile approach to art and science does a little body good. Let them throw their whole body into it with large hand movements when finger painting. One of the best tactile experience is clay and playdo. Playdo to start off with because it can be handmade and non toxic. When you are ready for hand print art for the purpose of a keepsake gift then you will need to take some control and help out.
Figure out if your child is ready to participate in art event before setting up.. Even if you have a infant she / he can make hand print art, so your child needs to be in the right frame of mind and awake. Make sure they are rested from a nap before starting. You want the art project to be a fun experience and not a struggle. If so, then creating hand print art projects will be a more enjoyable experience. It's wonderful if you have someone else helping out with project with baby's and toddler's if possible. Older children may not need as much supervision depending on the child. Tactile experience is such a fantastic way for child to engage and learn about the world around them and even better when you can keep it as a memento.