hm. signature quilts can be made with really large blocks - 10" or so. and the materials can be bold colours interspersed with muslin blocks for the signatures, so your upfront cost to make the blocks can be kept pretty low.
it would be a good sales tool to have something to show, an example sort of thing.
here's a picnic blanket i made for my daughter's teacher. something like this would probably work pretty well
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good luck! it's a great fundraising idea!
aileen