Thanks, this is very helpful. I suspect some of the shirts will not be cotton but we'll consider this when purchasing fusible interface. We will make sure we save extra tshirts in case we screw up. I like the idea of 15" rolls of interfacing. I use a table to iron on, so I'll take off the pad and we'll just have a sheet covering the table that should help with the fusing.
Here in California even warm & natural makes the bed quilts too warm for year round use but I do think that the Hobbs wool might be the right choice if its not too expensive. But why not flannel? It seems that would eliminate the back and make things easier. I'm not considering the fleece right now its just too stretchy to work with.
I am going to either have her or I do additional quilting on the quilt. I thought about having her do a grid across the t shirts but that sometimes detracts from the pictures. A simple meander should do it. I will also look at the different things you can do with a walking foot.
I think we will have a lot of help on this quilt as there will be four of us and a teenager working on various projects all at once. I'm hoping, with the teenager and my help, she can finish it in two long days.
Thanks for the suggestions.