@wjt I think the Internet Archive already has copies of these books, but you can double-check with https://help.archive.org/help/does-the-internet-archive-have-my-media/#:~:text=check%20if%20we%20have%20your%20media%20already
Otherwise, donating to charity shops is a great idea - apparently they make a profit even if the book gets recycled https://www.oxfam.org.uk/donate/donate-to-our-shops/donating-books/