Pull them out. Only set aside the ones you could realistically wear in a week and that still fit. Place the other in a pile and give them to your toddler for pajamas. Chances are your kid will love your old shirt as much as you did; Ty was pretty ecstatic about having Mommy-Mom's basketball shirt for her 'jamas. Especially if you point out the face of Albert Einstein and his crazy hair or the awesome player and basketball on it it is sure to be a hit.
No need to worry about where the bottom of the pajama set went or how to keep your kid in pajamas that fit because they grow too fast.
You might ask yourself how it can be considered a refashion without any work? The explanation is simple, by giving all of my old t-shirts to my toddler I am making a new and better use of them.