Acrylics ( the kind used in most kindergardeners classes) are quite safe, once dried. You can also cover the painted surfaces ( highly recommended) with a polyurethane sealer. I used on all my vivs, 3 coats of paint, and then 5 coats of the urethane. Now I have all the surfaces coated for ease of cleaning. I use a steamer to clean out the vivs on a weekly basis. After that, I just sop up the excess fluids with a towel, and toss that into the wash. Cleaning all done.
Janie.