as kids we gave each other floppy-disks.
...a text....sometimes drawings.
...a save with mission to complete.
We had a book where it all came together... it really felt like playing together.
The rewards were mostly candy. (I remember 1 time I got a VLB-IDE-controller with ram sockets for cache... I was a hero)
I really think this principal would work today as it did back then.