Very good! Thanks so much!
I googled and it's definitely a Polyphemus Moth caterpillar. I can see why it was hanging out in my front yard as it's eats both birch and maple leaves and we have both there so I'm sure there are more of it's buddies outside. Since we have a really nice mesh bug home thingy I think we will keep this one and watch it pupate and then release it back to the wild. They apparently overwinter in their cocoon.
Example of Polyphemus Moth caterpillar
Example of Polyphemus Moth
They kids have named him Chubby Lumpkins!
~~Joanna~~