SRegan:
If I ditch the idea of the clear water tube filling up, would this still be an issue? As long as there is still enough pressure when all 10 guns are active to knock the target switch, it shouldn't matter. Correct?
It'd still be an issue... He's saying the pressure to the guns would be equal. If you have a 25 psi back pressure and open up 1 nozzle, you've got 25/(area of 1 nozzle) of pressure coming out. That's gonna blast! If you've got 10 open, you've got 25/(10* nozzle area) of pressure. It might be kinda dribbly.
That sounds like a good option, but I did a quick Google search and could only find manual hose manifolds. Do you happen to have a link to some digital ones?
You don't evne need the main body, just the add on parts! http://www.amazon.com/Orbit-58874N-Extra-Complete-Watering/dp/B003LY4I2I/ref=pd_bxgy_lg_img_y
When that's closed, it completes a circuit to turn a small DC motor. he motor spins a long threaded rod ("Screw Drive") that you buy at Home Depot for $2. You have a little indicator ride a rail with a nut on the back... As the motor spins, the indicator rises along the screw! Have another feather switch at the top -- first one to hit the switch wins! (and it sets off lights/sounds/closes water gun solenoid/etc)
That sounds like the better option, I had originally thought that driving several motors would be more difficult than simply opening up some solenoid valves.
Have fun!