Why on earth would you leave 20% of your potential fun and safety up in the air? (granted thats a random percentage its actually lower than that)
You certainly don't need to upgrade calipers just to have fun.
However it is poor practice to say "you don't need the rears" or even imply it
Why? because the worst almost happened to me. Mid session at the end of the day I lost a rear pad. It just finally failed. Going into a 75 mph brake zone I had no right rear. Car damn near had a fit.
now i made a mistake. I looked at my rear pads from the outside only. had no idea the inner pad was gone.
Thankfully nothing bad happened but that changed it forever for me. My instructor and experienced friends all said the same thing...
"you left the rear stock?? Why?"
No matter the drivetrain you want to improve everything when it comes to brakes and tires. Like people who just put one tread type up front and "whatever" on the rear because its fwd (except drag racers)
Its not safe, not smart, and will hurt you in the end.
I'm of the mindset of if you can't afford front AND rear pads. You can't afford that track day then. Why risk it for no reason other than to save 80 dollars (a bit more in my application but ya know)?
I'm very passionate about this because I'm living proof that it makes a world of difference. Just cause its not a race doesn't mean you shouldn't prep like it.
You'll do great! Have fun! (I still use OEM rotors so no worries there)
Enjoy learning the track in the first half and look for pace later! If you can snag an instructor or a vetted track person see if they will work with you for a session to look for improvements or ways to make new "good" habits!
Where you going?