I would not drop price for same service but maybe you could offer two rate - one with meals included and one where parent supplies food. If most of your cost tied into the food cost, then if someone bring own food, then maybe you could reduce rate in that instance.

I not negotiate on rate or hours but I know cost of providing the service I do. Only way for me to lower price is to eliminate some of cost. Since can't lower insurance, heat, power, then food would be somewhere I could save cost if I not providing food.

I would be clear it all of nothing. Client not able to pick and choose to bring food one week and me provide some weeks. Client not able to pick and choose and have me give snack and them bring lunch. Either they provider ALL food or I provide ALL food. If they bringing food from home, then they need understand that if they forget it will need to go home and get it. I would not be shopping have having just in case back ups, that need to be clear not option.