everything the other posters have said, as was my immediate thought. But then I considered your points and realized that his choice of Lucy Steele means he is marrying himself as he had been mothered and sistered, so to speak. So he has this sense of fate about him, as if he feels destined to stay in that dominated position. I see another poster has referred to Lucy as possessive, and no doubt he has noticed this too. If this was so, he is showing a little bit of rebellion here, in saying what he does about his children.

I hope this makes sense.

IMHO, the casting of his role in S&S2 was completely inspired, as Hugh Grant really portrayed this sense of being powerless, yet being very mild in nature. (So not powerful enough to resist oppression.) I can't get over how harmless Edward (GR focus) is, and how personable, yet he is really, really, stuck. His comment about his children seems strange, given his resignation. If taken in the light of his acceptance of fate, this comment seems to bring out a little of the rebel in him, that does not seem to be there at all.