2 PS4s -how best to play BF4

I currently have Battlefield 4 (Premium) on disc on my PS4. My son got a PS4 recently (we're in the same house) and can play BF4 on his console since I have PSPlus and his console is my main one.

But what if we both want to play at the same time? If I bought it (again) from PS Store, would he be able to use my Premium DLC? Or what if I bought it (again) on disc -would that affect DLC one way or the other?

[To be clear, we can currently play all DLC on both consoles -I would like to know the most direct route to being able to play all maps on both at the same time ...bearing in mind the game is near end-of-life so I won't be buying all DLC again.]