Depends, how much do you like your family?

I see you've already decided to give it a go, but 3-4 hours out of every day is a LOT of time for a family man. I strongly suggest you listen to all the other good ideas on this page and consider shortening that time with a mixed mode (car/bike or transit/bike), or do only some days each week.

Another option that you should consider: move.

I used to live 25 mi from work, got back into cycling, and could only manage biking to work (2h each way) once a month or so. And even then, I would drive in with the bike, ride home, rest overnight, and ride back the next morning. 4 hours taken out of just one day was too much for me.

Also my kids went to a private school not far from my work, so my wife was making round trips up there once or twice a day (depending on carpools). I had been working there for many years, but after a few years of all the driving to school, I finally woke up and we decided to move to where our life is. We sold the 4br detached house with yard, and bought a 3br townhouse with no yard (and no yard care! yay!!). Now I am 5.5 mi from work and bike full time, and the kids don't have to waste half their life in a car.