Don't beg off because you've got kids at home. You're not the only one -- and by coming, you'll score points for professionalism.
Do try to meet new people. Now's not the time to stick with your usual lunch buddies; broaden your contacts.
Do some homework to find out what your boss's interests are so you can make some small talk. If she supports a charity, for instance, ask her how her last fundraiser went.
Don't talk too much about your kids. One cute story per child is enough -- after that, change topics.
Don't be conspicuous if you have to leave early. Say a quick goodbye to your friends and host, then head out discreetly.
Do relax and enjoy yourself. How often do you get a chance to enjoy some adults-only time out?