It seems like your kids aren't responsible enough yet for unsupervised bike riding, but maybe you could try something semi-supervised- you take them somewhere to ride bikes and relax while they bike around. Near our house we have a paved trail designated for people walking, riding bikes and rollerskating. It's set apart from residential areas so there's not really anywhere for the kiddos to wander. All along the trail are benches for people wanting to take a break, and there's parking at both ends of the trail so you can drive to it. Something like this would be great for you and your kids b/c they could burn off all that energy while you park it on a bench with a good book. Not sure about where you live, but there's trails like this scattered across ny and I bet other places have them too. Around here they usually call them "rail trails" b/c they are places where the railroad used to go through- they took out the rails, paved the trail and landscaped along the sides. You could try local parks, too. I know there are a few near us that have bike trails.