The average major league baseball game I would say lasts between 2 and 3/4 hours and 3 hours. I can't imagine it being a minor league game makes much of a difference.
Minor and Major have the same types of breaks - the breaks between innings and the break if they change pitchers. They don't stop major league games just for commercials.
Okay, I told the parents 4:30, so if the game is from 12-3, figure 30 minutes to have bathroom breaks and walk to the vans, then we should be back by 4.