Sounds great. I personally would wash the fabrics before cutting. If you are purchasing the denim (not using upcycled jeans) see if you can find a lighter weight one.
Regarding the business aspect, make sure you get a non-refundable deposit that will cover your outlay for the materials. Put something in writing, doesn't have to be real formal, maybe the size of the quilt, a description, total price and the fact that the deposit is non-refundable.