My photos are stored on my nas (omv), immich is on my android and I access it through wireguard.

My nas is raidz1 with 4 drives, so it is relatively resilient. The photos are backed up to a separate external hard drive too using borgbackup.

What i'd like to do is the following:
Back up my photos externally - at a family members house with a pi zero connected to a hard drive, which would be connected to their WiFi or via an ethernet cable to the router.

Ideally, the first backup should be done at home before, I don't want to backup 100's GB over the internet.

Would a simple wireguard tunnel be ok here? Should a different method be used?

Has anyone done such a thing? I read a lot about vps, but I don't what the ongoing commitment in cost when I have a free option.

One of my worries is that I don't want a compromised device on the family member's network to compromise mine, would the wireguard tunnel be enough to secure it? Would WiFi be more secure than ethernet cable?