Disagreeing is fine as long as you're not screaming, yelling, tossing bad words or insults around. It's good for children to know that parents can disagree and still love each other.
However, if things get heated, it's time to step back, cool off and try again. Remember, fighting should be about what's right, not who is right. If you're fighting to be right, even if your position is not sound, then it's a waste of time and breath. I would encourage you and your husband to agree on "Rules of the Fight," to make sure you're not fighting dirty, which can be very damaging to children.
When I was growing up, my mom and stepdad fought loud, mean and dirty. The fights usually ended with the police showing up (and me in trouble for calling) or my stepdad moving out. I was married for YEARS before I would ever disagree with my husband and, even sadder, it was years before I would sleep with the closet doors closed. I never wanted to hear a closet door slam open again. My husband had to teach me how to argue fairly and effectively. Because we learned together, when we do fight, it's clean and fair and their are (generally) no hard feelings.
Good luck!