lol! I've got no kids of my own, just an observation on what exactly gets the loudest complaints outta the Spongebob Set.
Just a 600 should keep three people satisfied easily. No problem. Plan early how you are going to control temps. A climate controller/environmental controller that has a thermostat and humidistat with actual outlets running off them lets you plug in a small heater that runs when temps drop below 68'F (or whatever you set it at), also plug in your biggest exhaust blower to run when temps climb above 82'F or so, or if the humidity goes over 45%.
Read the sticky at the top of the growroom setup forum that was written by Rhizome. He has a lot of experience setting up and troubleshooting all types of gardens.