Car for a Kid

I never thought I would be considering purchasing a car for my daughter to drive to school, but that is pretty much all I have been thinking about since school started three weeks ago. I always thought it was a little silly to have an extra car just for going back and forth to school. It seemed like a waste of gasoline since the school bus comes right to a stop near our house; however, this year the bus schedule is really messed up and unpredictable. My oldest daughter's bus comes at 6:29 am. School starts at 7:50. Even though the bus is scheduled to come at 6:29, it rarely does, so I send my daughter out to the stop and she stands there for ten or fifteen minutes in the dark until the bus comes along. Right behind that bus is my other daughter's bus that is supposed to pick her up at 6:43 am, but rarely gets there before 6:53. It is all very confusing and sets us all on edge in the morning. Because of all the uncertainty, I have been allowing my daughter to drive my car to school on days that I don't have anything scheduled. The only thing bad about that is that I am left without a car, and if one of the other kids (two others are in elementary school) gets sick or hurt, or something, I would be unable to get to them.
I have been secretly looking at used cars that are inexpensive, but safe and sound enough to get at least my oldest daughter to school and back on a daily basis. The problem is that while my daughter and I would go out in the evenings and on weekends to look, we would mention cars that we had seen on lots to my husband. He got the "car buying bug" and decided he couldn't stand his 2007 Hyundai Santa Fe anymore and went and bought a Cadillac Escalade ESV. That car is nice and it is great for all of us to finally be able to fit into one car comfortably, but that leaves us without any extra money to put aside to get a car for my daughter. I have been hoping to find something that we could just pay cash for, but it is very difficult. I hate to go behind my husband's back, but he doesn't seem to understand what a pain in the neck it is to have to guess about the buses, or to be left completely stranded for eight hours of the day. I found a car yesterday that is $1900; very clean, and it is from a reputable dealer. I told my husband about it, and he blew me off. Now I don't know what to do. I don't think I can go through the whole school year with either being stressed about the bus, or stranded. I need a car for my kid!