Diagram looks reasonable.
Instead of the PID on/off switch, consider using an ON/OFF switch for the panel which would disable the 120v hot to all components including PID, pumps, and SSR. This switch would have to be rated for 20 amps.
For a simple 120v element control, I have seen a few people using "sous vide" controllers from eBay in the $100 range. Probably cheaper than building a panel and you could wire a simple junction box w/ a couple switch outlets for the pumps.
Make sure you are using a GFCI outlet.