So the second circuit I tried to lay out was the vibration motor circuit. I used one that is fairly typically seen online with a diode and a small capacitor in parallel with the motor. My motor turned on, but I realized pretty quickly that it was going to be difficult to make the sort of effects I want.

Instead, I will probably use a haptic motor driver, which seems to be the usual response. Otherwise, I think I'd end up running in to weird timing issues, and I want to save processor speed for serial response as much as possible.