Ideas for centralizing two decades of my family's digital photos?

[fablefound]

hey, all! hope you're doing well. as the title implies, i'm a little stumped with a project as of late...

earlier this year, i got into my parents' old laptop, retrieving hundreds of pictures of family, friends, and my sister and i's baby pictures. amazing! i stuck them onto usbs and gifted the usbs to my family. foolishly, i thought that would be the end of it.

a second laptop emerged soon after, and i got that one working, too. thousands more pictures. managed to squeeze them all onto a usb. lovely again!

and now... my father has just handed me a third laptop and asked me to once again work my magic. i am, however, currently out of usbs. 

and this latest laptop has me wondering: what would be the best way to centralize all these old photos, rather than just playing hot potato with usbs? what can keep them all in one place and relatively accessible?

the first option would be just getting a bigger storage compartment, like an external hard drive. these are, however, boring and expensive.

i've been thinking about repurposing an old smartphone for the task: one with a lot of storage space, one that'd be easy to scroll through and pass amongst ourselves... kind of a digital photo album. i have an old iphone gathering dust in my drawer, and it could be a worthy test subject.

if that fails, it might be the external drive. but i'm curious if anyone here has any ideas for something i can put these photos on that'd be fun for the whole family 

[Slix]

External USB drive would be the most practical, but you could also use an old phone to sync those photos to it for viewing easily, so they're "living" on the external drive, but copied to the phone. Whatever you choose, make sure you have all of those important photos backed up somewhere else too! Having one copy on a single USB drive is not a backup!