A couple of things to consider:
For the total number of push buttons on the bars, count the "features", i.e. Turn L (1), R (2), Horn (3), HI/LO (4), Start (5). So in this configuration, you need a 2-button on one side, and a 3 button on the other. You can use a single button from the set above to act as "Start" and "Kill" by double pressing the button while running (Kills ignition). Momentary buttons don't toggle between L & R for turns, so that's why you'll need 2 buttons for that behavior. The M-unit automatically burns the headlight with the key ON, but suspends it while starting the bike. Pressing the button toggles to HI, press again, toggles back to LO. Holding the button extinguishes the headlight altogether.
Those gauges are fine, but you will need to run "diodes" inline between the TURN bulb on the gauge and the output from the M-unit. The reason is the gauge has only a single input wire to illuminate the bulb, but you have two "signal" wires (L & R). Without a diode (a diode is essentially a check valve preventing current from flowing in both directions) all turn signals on your bike will illuminate whenever either side is ignited. The diode will prevent "bleed over" of power from the "Left" side to the "Right". They're cheap, and easy to install, but required.
If you ever upgrade to a digital/electronic gauge, you may also need another button to act as the "Menu" toggle (MotoG gauges require this to scroll through the LCD screens).
If you use an M-unit, I'm a big fan of using a modern Regulator/Rectifier combo unit from Rick's Motorsports (model 10-100). You will need to retain the stock Starter Solenoid, but can discard the Starter Safety Motor, Flasher relay, Horn Buzzer, and Clutch Safety switch on your bike. That simplifies things a bit further for you on the wiring and space for installs.
