If you want or need to comply with standards and regulations, you most probably cannot use this kind of switch in the way you want to. This is because the switch probably doesn't meet safety insulation ratings between its two poles. Can't tell this from the datasheet, but usually these switches aren't made for your application.
So yes, it would be strongly recommended to a safety isolate the circuit by some other means (e.g. the mentioned optocouplers).
If it's a one-off for your personal use, I would hesitate a bit, but most probably just do it the way you describe.
Edit: No, I wouldn't, but for some other reason: The kind of contact used in these switches isn't made to work reliably on 3.3V ... 5V and a few mA levels. The contacts may get unreliable over time in your non-isolated circuit. One would operate them at voltages above 12 ... 24V. This is due to oxide or whatever coating that happens with this kind of power contacts, and this coating requires a minimum operating voltage and current to break through. 5V usually isn't enough.