How to secure your network in a VPN environment?

Hi, hope you're having a good day.

I have a tailscale network between my own devices.

I want to expand the use case. I have alot of relatives whom requires my techie love once a while. So I want to add them as into my tail scale network.

I'm not familiar with cyber security, what are the things I should do to make sure that a vulnerability on their PC wouldn't affect mine?

I'm hoping to eventually give them access to my NAS for cloud storage purpose, but I'll need to learn permissions control before I do that