Two of the things that impressed me about people in Montreal were (1) how cool they made being a parent look, and (2) how well they got their entire family around by bicycle. Moving around the city I saw the most impressive array of possible ways to use one bike to get around multiple people. People would attach posts to the center of the back wheel that one person would stand on while the other pedaled. Kids would sit side saddle on the top tube, while the grown up sat on the seat and pedaled. Smaller kids would balance on the handle bar, bigger kids would prop themselves on the back rack.
Flagstaff is a town full of bikers too. (Harley riders too, actually.) There are bike lanes to get around town, and there are extensive mountain biking areas, whether maintained by the city, or otherwise. I don't, however, see people getting their families around in atypical ways. There are all kinds of crazy bicycle concotions here--people that have built their own bikes in crazy shapes like the local guy who rides a bicycle that is a house story high, or the people that have constructed low riders with Harley style handlebars. But as far as moving kids around town, people take the traditional approach and put them on an extendo-bike, or in a kid seat at the back. The nine-year old and I decided today we'd get to and from school the Montreal way. She sat on my back rack as we bumped through town. At the end of it she said that she'd both never had so much fun, and didn't realize it would hurt her butt so bad.