Besides stamping the front, I used my Zink hAppy to print pix to wish them kisses and funny faces inside. Then I adhered a vintage valentine for some cute sentiment:
Here's a close-up of one to our nephew:
I included a little fruit wrap (though the girl got a Dunkin Donuts gift card) to give them something sweet but didn't bother going overboard since I'm sure they are going to get inundated with sweets by friends and schoolmates. And it doesn't hurt that it kept postage down to one stamp too. Just a little sweet something from their Auntie!