I'm one of the Latin course contributors and a Latin teacher myself. I just set up my first class and I'm looking forward to learning this new (for me) part of Duolingo.
It thought I'd start this thread so we can share experiences. If you post on this discussion I'll get an email notification, just in case you want to reach me about the course itself.
Any Latin textbook will teach you quite a lot. Deciding which is best is very subjective. I'm a fan of diving in without spending too much time worrying about which is best. When you finish, grab another book and use it to review what you just learned. Everyone has different learning styles, so not ever text will appeal to every learner.
The only textbook that I don't like is "Latin for Americans". I don't think it's a good choice for beginners. It's a fun and weird read once you've learned quite a bit.
I actually take Chinese AND Latin at my school, so I know that your best choice out of those three is Cambridge. I have used books one and two, and I am going to start the third soon. I would also suggest a Latin Dictionary. I use an Oxford Latin dictionary. It really helps. I don't know about the other books though.