Do your kids love nail varnish as much as mine? We use a water based nail varnish
especially made for children - no nasties and no need for nail varnish remover. It simply washes off with a little sponge or a soak in the bath and comes in great colours.
It also easily comes out of clothing, hair and furniture so we let them paint each other's nails... and we are finally getting to the point where it actually ends up only on their nails.