I think this is a great idea, and it's executed as well. My only worry is that I think it needs just a little something more... a necklace with a hand-print charm? I dunno. I'm just tossing out ideas.
I agree that it needs something more. It was VERY last minute! I think variegated floss would have looked nicer. I like the handprint necklace...you could use shrinky dinks!
...oooh or if you just get a hand-shaped charm and then made the chain with seedbeads and swarovski crystals in each of the grandkids' birthstone colors, or something similar. That'd be pretty. Or even if you just leave out the hand charm and do a colorful birthstone necklace. That wouldn't take long to make and wouldn't be really expensive, but it would add a little extra color and personality to the shirt. She could wear them separate or together.