Kate, re: the expired vitamins, my parents also have a lot of over-the-counter pills and supplements they buy online ... so many that they couldn't possibly take them all.
Check your city/county's website because they may have "household hazardous waste" drives where take all the chemicals and random things that you have in your house but can't throw away in the trash like paint, nail polish remover, electronics ... and pills/medication!
If you don't want to throw something away to a landfill and have it leech into the ground water, these drives are supposed to properly process and dispose of all kinds of potentially toxic things. You go to the location and you don't even get out of your car - they ask whether it's in the backseat or trunk and they're in protective suits and gather it for you. I've used it at least 3 times in neighboring cities and will likely keep using it as we go through all our stuff.
Hope that's helpful! Sending you positive thoughts and love through the universe ♡