I have done 8-10 tee shirt quilts which were no biggie. I usde contrasting fabric around each interfaces shirt piece and construct the quilt that way - differnet size shirt pieces wwere 'squared with the contrasting fabric.
I did one with jean pocket that was pretty cute as wellas runnign shorts and shirt . . . I only included the number part on those and used fusible interfacing with anything that had any stretch . that worked otu fine
The only 'interesting' situation I was confronted with was a mom(friend of my daughter's) who put in 3 receivng blankets. Unfortunately when I opened one of then up to use around one of the tee shirts - I found it was a favorite diaper and my entire sewing room spmelled like baby pee for a few day . . .
That was my only horrible experience - but all and all it was fun and I could let my imagination take me to new places - !
Just have fun with it!!