I am the mother of two girls, four and six, and have put off graduate school until they both enter elementary school. (My youngest will be in kindergarten in August.) Much like others in this thread, I am limited to only one choice for graduate school that also happens to be my undergrad alma mater. I've been a stay-at-home mom since my girls were born so, obviously, my husband is the breadwinner in the family and his career and the things it provides for (the mortgage, car payments and, basically, the necessities of life) depend on him staying in the same job in this area.
From the time we decided to have children (he was 30, I was 23) it has always been "the plan" for me to go to grad school. And although my husband works full-time, his position and seniority allow him flexibility so the understanding is that grad school is "my time" and its demands will come first in the family. (We'll have to see how that actually works out!)
It's nice to see people in similar situations. Until I found this site yesterday, I was feeling like I was the only one!