Thanks everyone. I will take all of this advice to heart.
I actually tried the ponying thing again yesterday, and decided that it wasn't so much that the mare was hyper (although she does get jiggy at times) but more that the foal was getting tired on the way home. He followed great going out, but would lag and sometimes stop on the way home. So I decided he needs a little more time to grow and get strong before I try to go very far. I will do super, super short rides with him from now on.
nrhareiner, I didn't mean to ride her too soon, I just thought some activity would be good for her. I was a little worried she would get more out of shape if I waited (not just physically but mentally), and when she had a vulva discharge a few days after foaling, my vet said he thought she needed more excersize. I don't have a pasture or large turnout area for them unfortunately. I can't even ride her and let the foal loose (which is what I would prefer to do) because of the dirt road and potential traffic. I live on a little neighborhood dirt road, but our property isn't fenced so I can't let the foal run loose while I ride.
What are your other concerns with riding the mare early? I surely don't want to hurt her, I love my girl.
My goal, eventually, is to be able to pony him out to the national forest and turn him loose while I ride his mom. I know we are a ways away from that, but I have a neighbor who does that with her weanlings and yearlings and they turn into great trail horses on that program.