A neighbor has a groundhog with 4 small babies on his property. He is trapping them to relocate. Beyond the point of whether or not he has the required permit, the offspring are small and I am assuming vulnerable. I read that they are ready for a den of their own at 5-6 weeks. They are out of the burrow eating, but each one is probably no bigger than a size 7 shoe. One is even smaller. Aren't they too young to relocate at this time?

Most litters are born in April or early May. So the ones born in April are moving out to new territories about now. The young you describe are probably pretty close to being ready to find their own territories. Hopefully the neighbor has a permit and knows not to release them in a park or natural area (which is illegal).