I'd bring as many as possible and "preloaded" if possible, I'd check first. Since some drills don't require a full mag.
It sucks when you/we have to wait on the line for someone to reload.
If it were me, two mags are on the thin side for a class. One mag could go down, you never know. IMHO, I think if you do take the class with only two mags, you'll be wishing you brought more. I'd want your first class experience to be an enjoyable memory and not a time where you spend more time reloading and not paying attention to the instructors since you're worrying about your empty mags.
ETA: I remember one class, I brought about 40ish mags loaded. It was great not wearing out my thumbs and taking a breather while everyone topped off mags as fast as possible.