Yup. If the sd card doesnt have enough space for everything, you could attach an m.2 hat to it as well. https://www.raspberrypi.com/news/using-m-2-hat-with-raspberry-pi-5/
Basically, jellyfin on the pi, with the wifi setup as an access point, and whatever amount of storage you need. The pi requires 5v/5a, so you’ll probably run into issues running off the car usb power, but a cheap 30amp hour battery should run it for 6-10 hours if my napkin math is right.
As a reference to the Santa clause?