Is it ever OK to reimburse small cash purchases without a receipt?

We are a really small- 25 active members-, rural church in NY.

Every month for the past 20 years we have hosted a community luncheon for the elderly in our area and usually have about 50 attendees and 15-20 take out meals.

The same volunteers usually cook and bake; usually preparing a lot from their home kitchens and it is "from scratch".

One doesn't go out and specifically buy 2 1/2 cups butter, 6 C flour, 3 C chocolate chips, etc. so there isn't a receipt.

Many of the cookers/bakers just donate the ingredients, but for some their time is really the gift and they can't afford to do this month after month without getting reimbursed.

Trust and working together for the good of the community is what our church is about and yet we want to have legal accounting practices. Any suggestions? We would surely appreciate it!