Somewhere around here, and around the net there are instructions on replacing the font on the K2 with one of your own choice. I've found it quite easy. I guess you have to be technically-orientated to do it, but in this case I think its more an issue of being willing to do it, not a true technical barrier.
I suspect that your grandma may not be that adventurous but its something you might want to look into. The only downfall that I am aware of is that your Kindle may not automatically apply new systems updates (these are quite infrequent) until you remove the font patch. After the update you can reapply the patch.