We talked about this briefly last semester at St. Vlad's Seminary. I think the main idea was that there is no real theological reason why a girl couldn't be brought into the altar. The main points we were encouraged to get across in our parishes in the future:
1) Whatever you do in regards to "churching" children, be consistent. I think one way to go is you either bring both into the altar, or bring neither; one or the other - just do it at the royal doors and before the icons of the Lord and Panagia. I think it will depend on local practice. Think about it, if you're a newly-ordained priest and you get assigned to a parish and see something you don't like (for example, the way the parish has practiced the "churching" of a child), and you barge in and start changing things right off the bat, you probably won't last long as a priest. Gradual, slow, teaching is the way to go about it. Either way, I can't see a huge issue in it; we've got bigger fish to fry in terms of Orthodox faith and life, especially in America.
2.) Never "church" a child after they've been baptized. It doesn't make theological sense to bring them into the church through baptism, then take them symbolically "out" again and then back "in" when you church them. Always before baptism.
Plus, if you think about it - and this is in my experience -, most people who bring their child to be churched will probably only darken the doors of the church a few times a year; they don't know what's going on anyway, and if you try to explain it to them, they probably won't pay too much attention. For most of the "minimal" Orthodox that I am referring to here, the churching is really about a family event and gathering, especially in regards to the ethnic Orthodox populations. However, I realize that this generality can't be applied across the board, so again, a priest in my view needs to pay attention to the practice of the community, the instructions of his bishop, and go with that. Just be consistent about it, whatever you do.