I'd have to agree with Duncanjp. Is it possible to commute three hours, raise kids, and still succeed in law school? Yes, but it's going to be very stressful. Law school is nothing like undergrad, it's far more difficult and time consuming.
I had a family and went to law school at night. My wife was already a lawyer and thus was more understanding than the average spouse. Even so, it put a strain on our relationship. For four years my evenings were spent in class and my weekends were a balancing act. I opted to spend more time with my family than many of my classmates, especially after the first two years. Nonetheless I still missed out on vacations, weekend trips, you name it. More significantly, a huge amount of the daily running of the house fell squarely on my wife, I simply wasn't around.
It's imperitive that you get your spouse fully onboard right from the outset. Especially if you have kids, this is going to have to be a serious team effort for the next few years. If there is a way to avoid the commute (a closer school?), do it.