If you decide that you would like to have a lighter summer, what you could do is tell her you will only charge her full fees for xmas and march break and let her take the child out for the summer and hold her space over the summer with a deposit. You could go further and tell her she has to pay for xmas and March break without bringing her child in exchange for you holding her spot over the summer. This way you get a little paid holiday at those times. Don't forget to take a deposit to ensure she returns in September.