Why not do a ten minute block for each mug. You will end up with 4 triangular pockets for the children to fill. Hope you understand what I mean as my head not working this morning.
Are you being paid as it willwork out financially very expensive plus time consuming. Don't be a doormat go and chat with the head about your concerns. A few for friends and so many and it could snowball from their. Ask how I know I was a teacher but also the head and only sewer in a school slightly larger than yours. I would cost using charm packs when you see the head and that the cost is only one side still need batting and backing. Small schools usually short of money . Another quick make just thought about is just a square but fill with bit of smelly stuff so that when heat placed on you get the aroma. These could be bagged put with one side not sewn for filling and how about a quick loop.