Multiple PeerId's

I am trying to create a multi user app where all users to the system have their own MFS directories. As i understand it for privacy all users would need to have their own peerid and private keys would remain secret to other users. There could be hundreds of users at a time using the system. Is there a way to pass the peerid along with the API calls?

stack and libraries
ipfs cluster
react native

What you’re describing sounds like a web portal to IPFS generally. Is there a need for PeerID’s in this scheme? The directories are still just IPFS blocks that can be replicated and or pinned anywhere.