Love this minus the cat! Get the kids to paint background with watery paint and scrunch paper. Carefully uncrumple and lay to dry. When dry have them draw a tree branch with a black sharpie and glue on a black cat made out of paper.
I created this paper plate black cat for kids because as far as Halloween characters go, I think the black cat is commonly overlooked. Tap the link Now - Luxury Cat Gear - Treat Yourself and Your CAT! Stand Out in a Crowded World!