I took the SIG academy Patrol Rifle Instructor course (5 days) and max distance was maybe 75 yds but the qual was 50 yds and in so irons would have been fine. If your class is similar here is my advice:
Red dots were common but I would rather use irons over a red dot unless shooting in low light. I used a Leupold CQT (1-3x with ILL). I used/use a Vtac sling because of the quick adjust feature. The instructors (and I after day one) mounted the butt side of the sling to the right hand side of the rifle to allow seamless transition to weak side shooting. So whatever sling you choose make sure you can transition to weak side if required by the course. If there is ever a time for a "battle belt" this is one. With a battle belt you can mount (and it will support) a dump pouch, plenty of mags and a pistol if needed. Chest rigs were used by many (cops mostly) but were much slower on the reloads and prone shooting was not so good. A battle belt can be worn outside whatever clothing you have to use vice fighting to reach normal belt mounted mags under a jacket. Take plenty of mags so you can load and stage them with your pack, that way when you take a break you don't have to reload mags just grab more. This gives you time to grab a snack/drink and shoot the bull. I had to improvise a battle belt by wearing a larger size instructor belt on the outside on my jacket. While it worked, the support of a battle belt is superior and is what I use now for these type classes. It also allows you to easily dump the rig for lunch or a break. I mentioned dump pouch, if there is one piece of gear I would take besides the rifle, mags and ammo it would be a dump pouch.