Make a list of these books on your blog, or make a video, or a Goodreads shelf or post a picture on Instagram—whatever is easiest for you. Then get friends, other bloggers/booktubers etc. to vote on which books you HAVE to read.
When the readathon comes along, you read the books in the order of most votes. For example, if one book gets 10 votes—you read that first, then the one that got 7 and so on. If there's a tie, then it's your preference. The goal is to read as many as possible.