grounding switched power question

I’m using the laser module. Pin 2.6 works OK, M106 and M107 switch it on and off. Pin 2.4 switches OK at the header (3.3 V), but at the connector at the board edge it acts oddly, the status LED is half lit.
The PWM output on pin 2.5 at the header works OK.
I’d like to use all of these with a common ground. This could be done with the header, but then I’d have to switch power myself- not an impossible thing. But would it be possible to run them from a common ground without toasting parts?
Only one of the outputs needs 12 V power for my application, the other two are just 3.3 V signals.
Any thoughts would be welcome.
This is not for a printer, CNC or laser cutter, just a little science project.

Imported from wikidot

Did you ever find a solution ?

The mosfets use a common positive and the grounds are switched.