If you're in VR, just use your VR hands to hit the buttons. In desktop mode, I do this:
1) Add a sphere (add atom, shapes, sphere) to your scene and make sure collision is on. (it's on by default for me)
2) Resize the sphere to about the size of the button and move it so that it is right in front of the button.
3) Rotate the sphere so that one of its three axes is going in and out of the button. If it's already aligned, then just leave it.
Now, to activate the button, first, click on the sphere to show its 3D cursor. Move your mouse to highlight the axis that corresponds to the in and out direction, then just drag the sphere to hit the button.
Basically, you can just use any object to hit the buttons as long as collision is on.
***EDIT***
For the creampie scene, you can also do this. Forget about the button. You can even delete it if you want.
Goto:
actor1
Collision Triggers
LabiaTrigger (click "Actions...")
Click "Add Discrete Action"
Click "Settings..."
Receiver Attom (change none to actor1)
Receiver (change none to 50s_CreampieSim)
Receiver Target (change none to reset)
Now you can just use the dildo to touch her there and enjoy your creampie.