I would think up some easy meals and work backwards to get the grocery list. Baked ziti, tuna casserole, chicken and dumpling casserole, etc. Then build your ingredient list, along with staples. Milk, cereal, peanut butter, bread, etc.
wonderful thing you are doing.
Maybe bake a few treats every few days to send home to the kids. Easier for you to bake than having to worry if they've got the small amounts of various ingredients like baking soda, powder, flour, sugar, butter, chips, etc. Plus I find this good time to meditate and pray for the person I'm baking for.