Old thread but this takes me back to my childhood (when I was dragged to open houses almost every weekend between about 7-10). I hated it then (my parents had no intention of moving or buying another house, they just went to open houses for fun) and honestly I don't see myself ever buying a home. I had enough with the home stuff in childhood to be happy in an apartment for the rest of my life.
Until you are a serious buyer of a particular home (follow-up visit, etc) consider making alternative arrangements for your children as it is not the most age-appropriate activity (babysitter, playdates, grandma time, etc). This is a benefit for you, the children, and the seller (they won't run wild).