I've been to Le Mans twice with two of my boys, in 2008 aged 8 and 10 and last year 10 and 12. We camped at BSJ both years. They had a great time! There are many drunk people at BSJ, even a few without pants on (or clothing at all), but nothing to worry about. I know parents are different and I'm probably more liberal than most, but everyone's extremely kind and helpful to the kids so I've never felt we were unsafe at all.
That said, however, they were quite annoyed by the mopeds running during the night close to the tent. A Corvette is *music* in comparison! So this year we're staying at Mulsanne and have booked a park ticket in Green area. With careful planning we expect to have a great time. Of course my intake of beer will have to be confined to times when I'm not driving the car, but I'm sure 2011 will be the best Le Mans so far for us.
/Anders