Grand canyon South rim stay over

[Drino]

Hello all and thank you in advance for helping me out..we visiting grand canyon my birthday thanksgiving. Still have el tovar booked but at $220 for one night..is very expensive.After sunset approx 5.15 we'll be back in room for 9pm after dinner at el tovar again expensive! Then out for sunrise early...i'm looking at a $18 tent pitch at Mather campground but were not campers...its one night right lol? Temperature is like -4 late november...could i not sleep in car at my paid tent pitch?

If not ill have to rent a tent for $16 or get one from wallmart...then i need couple sleeping bags...tbh' $50 outlay is nothing compared to what they want for a night in a 2.5/3 star hotel...any thought please