Yes, I'd say that Lady Middleton had every right to be preoccupied by her children! Personally, I've always found a small baby easier to look after than one who's old enough to get around by itself (except when the baby is collicky or teething, of course!). I'm reminded of this passage from our group read of Amanda Vickery's "The Gentleman's Daughter":

Even with the help of a servant, it is evident women found their responsibilities [as mothers] all-consuming, leaving little or no time for the pleasures and activities of spinsterhoood or the honeymoon years." (p.110)

The production and rearing of children had a transforming effect on genteel women's lives, all but obliterating their past selves and public profile. (p.122)

I'm rather puzzled as to what JA's true attitude towards children was, and I'm still trying to figure it out. On the one hand, it's clear (not just from S&S) that she had little use for children who didn't meet her standards of behaviour, or for excessively child-centered mothers, which makes her sound a bit like those obnoxious people who know exactly how *others* should raise their kids.