I would use a very thin batting, the kind of batting you use in table mats, (warm and Natural light wt.)
Because you are useing the Yellow brick road pattern, You will have alot of seams for your blocks. I would think you would want to add the little bit of thickness from a light weight batting. Goood luck, I love the Yellow brick road pattern., I am just finishing up a baby quilt for my niece with that pattern.