I had something of what you are planning years ago...At the time I was living in Colorado and I wanted a moonlit night scene of an Arapahoe Basin Ski run with a skier registered in the scene. What I did was set my base exposure based upon metering the actual scene for about 2 minutes (including reciprocity considerations) and had a sound trigger set to trip the strobes as the skier came to the proper position. The reason for the use of fill light was that there would not have been any other way that I could determine to stop the skier and register the proper exposure of the surroundings. I wonder if you might not try something of that nature for your planned shot. No need for a sound trigger. Just manually trigger the strobe and use ND filters to give you a long exposure. Determine your strobe ratio balanced to surrounding scene to underexpose the figures of the boys. If you use color film I might mention to be aware of color shifts based on reciprocity considerations. Hope that something in all of this rambling will trigger a furthering of your idea. Good luck.