jacket BCD is the only reasonable option, your instructor trainer is correct. There will be nay-sayers and differing opinions, but when it comes to skills demonstrations, trying to show a student the correct way to use the equipment issued to them is most effectively done with equipment that is somewhat similar in function AND appearance to theirs. If you are looking for simple and sturdy, consider looking at the rental kit they are actually using. That kit is subjected to harsh and careless use by students and guests on a daily basis. If your kit is cared for better, imagine how long it might last. I have worked with seaquest, DiveBuddy, and Scubapro and all of the BCD's constructed with an eye towards rental fleet market will show a tendency to survive.
I personally spent a lot on mine and am willing to pay more often for the extra comfortable poodle jacket. I use a mares dragon (both here in cold water / drysuit, and in tropical waters.) when you fully inflate the dragon, it pops you so far up out of the water that your hands are completely clear... great if you like to use hand gestures while you speak.
For fins, I have used several (both splits and solids) and none worked better for giving the traction needed to catch wayward guests and attention deficient students than the Mares open heel with 3 or 4 "channels". I love the stiffer feel, and when you are in water 3+ times per day, your legs WILL get strong enough to make use of the extra traction. Split fins are like riding a bicycle in the easiest gear: if you are willing to "peddle" like crazy.... That has been my experience and is MY OPINION
good luck on your course, and if I may offer a bit of advice: DIVE. Dive lots. Dive some more. Get as much real experience as you can before you go out and start teaching. You will be the better teacher when you have a feel for how and why whatever happens as it does, and how to deal with it, when you can call upon personal experience from having seen some of it personally, than you ever could from reading about it. You will be a more confident teacher with more to offer your students when you start teaching.