Getting a ton of cards can get expensive real quick, and if you don't have a good way to store them, can be easily lost. Getting a few cards, a cheap laptop/tablet (you already indicated you have one not being used) and migrating them over to a portable hard drive is the best solution IMO. It may take some time to do the migrating, but you have one drive the size of a paperback book instead of 15 little cards scattered around.
I've never done research on it, but I wish there were a big hard drive that you could just plug your card into and it would automatically transfer the files. A green light comes on when it's finished, and you go on about your business. No wires or 3rd party devices needed. (There's probably something like that already)
EDIT:
Here you go! I bet you can find one out there much cheaper. Just search "portable photo storage device"