I've spoken to my wife about this push to get Theron baptized, or indoctrinated, or whatever the precise goal is. Her initial reaction was fairly neutral, along the lines of "Sure, whatever."
So when Nana (my wife's mother, who's a minister for the Disciples of Christ) stopped by to drop some things off, I asked her what she thought about it. I was... pleasantly surprised by her response.
She said, basically, that she thinks he's too young. Baptism now will be much less meaningful than baptism him later, when and if he chooses it for himself. The dedication ceremony probably isn't what we want, either, since it generally requires the parents to promise that they'll raise the child to be a good Christian. She basically laughed off the idea that if he died unbaptized, he might go to Hell. I'm not sure that the Disciples explicitly reject that belief, but they certainly don't endorse it. Quoting from memory: "We don't believe babies are born evil."
She also said that, as Theron's parents, this is our decision to make. I've put that in italics not because it's an important point to me (though it is), but because she was fairly emphatic about it.
More than anything else, I think I was surprised that Nana's views are so much in line with my own - what with her being a minister, and me being an unbeliever. We're obviously coming at the question from different directions, but we're arriving at the same place. Her other points (about dedication not really being appropriate for us, and about this being our decision) were well taken, too. And the sorts of things that I thought she might be concerned about... well, they don't really concern her. In particular, she doesn't think it will be a huge crisis if he does get baptized in the Episcopal church, she just thinks it won't mean much (if anything) to him right now.
So, um, mad props to my mother-in-law.
I went back and relayed that to my wife (who wasn't a part of the conversation only because she was bathing the boys when her mother arrived). She agrees whole-heartedly: we'll both be a lot more comfortable waiting, and letting Theron choose for himself. Which was pretty much the plan all along, thank-you-very-much.
That's still going to create some friction, I think, but it'll be the sort of thing that's best addressed by looking at how my parents handle having Theron at their church. Which is going to be an interesting conversation in its own right, but at least it's not going to require us to reconcile disparate views from various parts of the extended family.
So, to recap:
1. Talking to my mother-in-law was enlightening and helpful.
2. Firstborn is not getting baptized until he's ready.
 Not her real name, obviously.
 The Disciples of Christ have quite a number of issues where their official doctrine is, basically, "The scriptures don't give a specific directive, so you'll have to rely on your own conscience and judgement." In their words: "Where the Bible speaks, we speak. Where the Bible is silent, we are silent." Since a lot of the more questionable - and problematic - elements of Christianity seem to me to arise from people trying to fill in all the blanks for themselves, I rather like this approach.