Preferred method for removing mold & mildew from album covers

Check out eBay - your source for album covers in great shape and LPs inside in crappy shape.  Good luck.

The other alternative is to not worry about the covers for now, and buy some high grade plain cardboard jackets- I like the white ones with the cut out in the middle sold by sleeve city. I use these in connection with new inner sleeves for repacking some records after cleaning. If you want you can write on the jacket in indelible marker or use a sticker (i do the latter) to better identify what’s in it. They offer pretty good protection as well. Mine are usually then bagged as part of a larger package for each record, but you don’t have to be obsessive about it. 

Good suggestion whart.  I'll be doing this.

I would throw them all away. Even if you somehow manage to clean them, you will never be sure that there is no mold left there. And that's the kind of caca you don't want to keep around.