SRegan:
Is there any solution other than having an individual pump for each gun?
yes. get a tarp, get a hose. get a timer and start quirting. drain the tarp and measure how much fluid you need for one.
get a water heater of the proper galllaonage, (make up words as you go along) get an expansion tank. read up on how to charge the tank. the expansion tank will keep a somewhat consistant pressure and the pump running at the same time will replenish as you go. you this is all home depot stuff. you might be able to just get a large enough pump ( or use two) that will keep up.best way is to get 10 nozzles, 10 houses and those 2 dollar shut off valves
http://www.dripirrigation.com/drip_irrigation_categories/75/drip_irrigation_parts/54
get 10 sweeper nozzles
http://www.amazonsupply.com/dixon-psn76-sweeper-nozzle-orifice/dp/B00835N7MMtry one, then two, then three.....
get wet, have fun, figure it out.