Using a blanket stitch and embroidery thread, I attached the dino to the t-shirt (I used a small bit of washable pritt-stick to keep the dino in place while I stitched). It has been a while since I hand-stitched something, and the slow repeatable motions were quite relaxing.
And much to my delight, this tee has also been approved by the little man, who is such a busy little bee, it was hard to get a "non-blurred" photo of him wearing his newly acquired tee-shirt.
I was worried the felt wouldn't hold up being washed (for the first time) in the washing machine, but I just turned the t-shirt inside out and put it in a lingerie wash-bag so it wouldn't be rubbed against during the wash cycle and it came out fine.