I have created a first sketch in KiCad of how I imagined the circuit would work, and uploaded it as a ZIP archive. First I added a power section which will take the 24VAC from a 120VAC transformer and then rectify filter and regulate to 5V to power the RasPi, then I added a MOSFET relay control section which will actuate the solenoids in the water valves. I need to learn more about how to control AC with MOSFETS, so if anyone has any good guides or circuit examples it would be greatly appreciated.