Well I hope all the Parents in the Coach Boats read and head the sailing instructions! I don't want to get run over by a "Coach Boat", or have to duck one either.
Perhaps they could set up a "Holding Pen" for the coach boats, about 500 yards below the start/finish area, and make them all stay in there while we are starting and racing.
Thats exactly what they do for Opti regattas now, works well. Coaches have to stay below a line of marks that is parallel to the start line until the RC drops orange flag, at that time you can ONLY go up the right side to windward mark (with "right" side being marked by more small bouys or a "pacer" umpire boat). If you want to go to the finish line (the finish line is off to the left), again, you must stay outside of marked area. A bit of extra work for the RC, but man, makes it really nice for spectators, coaches and racers.
Keep in mind 10-15 year olds need a bit more support on the water then "go left or go right", coaches (and parents) play a huge roll in making the sport fun and a positive experience for the racers.
(I should mention all motor boats, coaches, spectators, etc have to be registered with RC on land and get a flag with a number for identifying. This number is also associated with what sail numbers they are coaching / supporting for several reasons, one is safety, RC knows who to call when someone needs help)