J.S.
I have painted pumpkins with many children many times. I took the advise of using washable paints (water based) versus acrylic paints one year. As the pumpkin begins to dry out so does the washable paint, then it flakes off. So I wouldn't use washable unless you plan to do it within a couple of days of Halloween. Acrylics work great without any trouble. Hobby Lobby carries them and they range from about $1 a small bottle to around $3 for a large bottle. Unless you have a large group, the small bottles go a long way.