Heres my take, Think throw size,I would use only the T-shirts, cut them apart, from fronts and back cut as big a sq. as you can get, stabilize these sq. then decide what size block you want to cut from them. Do some photo transfers of your aunt and uncle and use these with your blocks.A simple 8" block w' a 2" sash and your home free.
If you feel you must use the pant material, use a piece for the label cut in the shape of ( you got it) the pants.