Hmmm, I always used to play in the cul de sac when I was little. Probably why childhood obesity was all but unheard of back then. So did my DP actually. There's really not much traffic in cul de sacs at all.
Heck, down the road from my house there's always a group of young children playing on the street and I'm not even on a cul de sac and yes I (and probably most other responsible drivers) DO keep an eye out for children/pedestrians/dogs/cats and whatever else may be on the road.
Annoying about the car, absolutely, but I dunno.... I don't think a bit of playing in a cul de sac should be considered neglect.