You need to step back to square one.

Your MCU GPIO pin needs to supply 7-10mA at what voltage?
Can the MCU pin drive the load directly?

 

Can the MCU pin drive the load directly?

I would have preferred that, but like I mentioned in my post, I will have parallel switching requirements. The load is actually a relay switch rated at 24vdc (150mW), so I would ofcourse need a logic level shift. Plus the MCU (STM32 or thinking about adding a shift-register in order to keep count of GPIO pins in check) might not be able to deliver more than 70-80 mA, while I can have 9-10 relay switches (as load) that would be an over kill for the MCU - taking into consideration that the MCU will have some sensors adding to its workload.

 

I think it'll be somewhere around 7-10 ma.

Okay, then it depend upon how much current you can supply to the input and the minimum transfer ratio of the opto, as to whether you need the added transistor.
The maximum input and output current is 50mA and the minimum transfer ratio of the PC-817 is 50% so you would need a minimum of 20mA input current to directly drive the output load.
If you can supply 20mA to the input then you shouldn't need the added output transistor.

 

You don't need a level shifter. What you need is an output driver transistor.