In some states, the sprinkler guy keeps his grubby hands off the potable well water supply of a home, and he never thinks twice about it. I don't care for the 60 psi top limit for the inline plastic CSV. Make a brass inline with 1-1/4 inch female threads and a 70 psi top, and you might have something that could even fit steel drop pipes. But back to the dozen trees, it's easy to set up low-flow drip to run concurrently with other zones. No further worries except controller setting. It might be easier to set popup sprays to drench the tree area with the 18 gpm, as that can be handled by any controller whatsoever.