Over the years I have done food a couple different ways. One is making out a 3-4 week sample menu of typical foods and costing that out to get a per meal cost.

The other was doing the total food bill and total meals served to get a number and in reality there was only a couple hundred dollars difference between the two methods. For me doing the total bill and average people fed is the easiest. This allows you to take into account that you are serving last nights supper to the daycare for lunch as in that meal served one family plus 4 kids.

I just add up all the grocery receipts for the year to get a total. Then look at a typical week of how many family meals are served - take into consideration do you or hubby eat a full breakfast or is it more like a snack not a meal, does he buy lunch at work or take one from home. Do that for one week. Once you know how many times you serve per week it is easy to divide it out. And it is the easiest way if your own kids are also in the daycare since their meals served during the week don't count as a daycare expense.