I got in touch with the step-mum and she picked the layout, fabrics etc, and I finally got round to putting it altogether.
I've got the top done already, but I can't find my large quilting needles so I have to wait till I can get my hands on some before I start quilting!
I like to use a very sheer interfacing on the backs of the tees (Pellon 609F is my weapon of choice) because it's easy to use and it's super thin so it doesn't make the tee all bulky. The reason I bother with interfacing is that I like having the fabric stabilised so I can get everything cut and sewn accurately. Definitely worth the little bit of effort to make everything lay perfectly flat!
Also, if you're thinking of making one, I suggest you wash your tees without softener before doing anything because the interfacing doesn't adhere as well when there's fabric softener in the equation.
Going to think about how to quilt this... Hmmm...