I'm not sure I'll be too much help, since I have not created such a group myself. However, my mom did, and I am a part of a young group and friends with that group's creator. So I know a good bit about it secondhand, at least...
The big thing is to find other like-minded parents to help. What's the old saying? One person is a crank, two are a nut and her friend, three are a group, and four are a movement...or something like that. You want to be a movement, not a couple of nuts if you can.
Plus it will take some time and effort to get a group started, and trying to do it all alone--especially with a new baby--would not be very smart! Having a core group who are there regularly will keep things from stalling out, too. Nothing ends progress like a mostly empty room for a meeting. People don't come back if they see that. Recruit people who will show up and get help wherever and whenever possible.
Also, it's smart to ask people what fires them up. If you want to attack the problem from the perspective of individual teachers, but someone in the group wants to lobby Congress (or whatever), you're not going to get very far on your specific goal. Be sure you're enabling people to make the progress they think matters.
Finally, I'd recommend starting small. Better a couple of short-term goals you can achieve (though presumably in the framework of larger goals) than some grand, huge ideals that scare people off because they sound like so much work.
Dunno if that helps...
