I think you have a great idea. In Florida, we have quite a few of these:
http://www.bikely.com/maps/bike-path/cheating
It gets the kids over the canals on the way to school, without forcing them into traffic. Of course, it works great for the bike commuter, like me, who would rather not ride in traffic.
Approaching it as a solution for the kids might be an easier sell. I think it will still be a long time before bike commuting gets the respect it deserves.