Every walk site is organized differently. It is usually 6.2 miles (10K). Ours is set up to be a large circle around Plymouth waterfront (beautiful setting). Two laps around is a full 10K. Many people go around only once. It is very lax like Melissa said. Some sprint, some rollerblade, some stroll and shop along the way. Don't forget, its all about the money.
My kids have always attended since Josh was a year old (he'll be 16 at this walk)Except for last year when Josh was so sick, they walk at least once around. Its a great social event for them, they have family and friends to hang out with. For them, its not about the fundraising or the disease, its about being a kid.
We don't worry too much about interaction with other CFers because it is outside and my kids stay away from the mixed group at registration and the post walk cookout.
***Just a word of warning to the parents. I find this event very emotional. I usually weep throughout the whole thing. The support from both my team and other team leaders that I've gotten to know over the years is so encouraging. But again, I can't ignore the reason we're all there in the first place. <i>This event is for MY kids because MY kids have a nasty, life-threatening disease. </i>Its a tough day.