First, in your shoes, I might advocate to a switch to a "White Elephant," where everyone brings a goofy item they already own to exchange. And then people can go through a swapping process if you want. It's so fun!
But if the generic $20 gift is something your family is into, my suggestions would be...
* a nice insulated food jar that can keep soups/stews hot for long periods
* a homemade pie? (and seconding the recommendations of other consumables like honey or maple syrup)
* since this is family, maybe a photo book, like the ones from Blurb, where you gather a bunch of digital or digitized family photos and have them printed in book form. You could add in some text about the memories you have shared.
* a cheap bluetooth speaker (I received one of these as a "cheap generic gift" myself. I LOVE it and use it almost every day for my podcasts).
Regarding wrapping paper... I've wrapped gifts in brown paper from grocery bags before. I decorate them with stencils so they look festive.