how to make ground beef go further??

so i planned my dinner meals for the next 2 weeks and i have 4 dishes that call for ground beef. i normally use 2 pounds to feed the family (4 adults,3 children) and have a little left over. i read i can add beans to the meat but i don't know what kind.
the 4 meals i'm making are sloppy joes, cream of mushroom hamburger, hamburger curry and Korean beef

black beans and pinto beans go good in almost anything imo. lol

Beans, mushrooms, grate up zuchinni and carrots in there and it makes more.

stuffed peppers  

i have added oats before