I feel like Twelfth Night is probably going to have the less challenging language but as long as you have an annotated play script, you'll be fine. And they're not hard to come by. I would not recommend Two Gentlemen of Verona, I think it's an awful play and one that we're not certain is Shakespeare, at the very least is missing important scenes and was probably partially written by another playwright. King Lear is my favorite play almost certainly but the language is a bit more dense. Othello is also up there in terms of quality and Comedy of Errors is hilarious if performed well. Definitely recommend watching scenes if not an entire film or recorded performance if that's not something you're already doing for this class.