Disks are not designed to be usable after 5-10 years of sitting on a shelf. Portable drives aren't particularly robust either, I've worked with many people with lost data on a USB attached drive. I'd use at LEAST two drives, ideally in two places if that's your only store for anything important.
I'd recommend using a cloud service (amazon.com/Amazon-Photos/, https://www.flickr.com/, https://photos.google.com/) or similar AND keep a local copy on a disk. Plan on replacing the disk every 5 years and paying whatever monthly/annual fees for enough photo storage. Include in your will full details on the online and offline access to the data. Sure it's a pain, sure there are costs involved, but it's not some insurmountable task. Much like your taxes, will, deeds for property, bank account info, etc. In all cases you want the original documents and pointers to the company/account.
Bitwarden (among others) handles designating a successor for accounts in the case of death, you can include username, password, and any encrypted volume info there.
