It can be okay for parents to fall into a disagreement in front of their kids -- who are we kidding, this isn't a perfect world. When they do happen, family arguments can be an opportunity to show your kids how to communicate. You can be the role model by putting your constructive rather than destructive argument skills on display.
The art of arguing includes staying calm, being respectful, dealing with the problem and completing the argument, even if it means taking some time away (time out for parents). When you do argue in front of the kids, be sure to apologize and make up in front of them too.