The best thing, Joe, is to only feed them chick feed. It's a balanced food and does not require you to try to match the grit volume with the "treat food" volume. The danger with grit is that a chick can load up on it and gain no nutrients. When my chicks get into their adult/adolescent food and require grit, THEN I'll feed them other kinds of food including insects and meal worms.
My chicks are at day ten tomorrow.