My DH and I went on a 5 mo roadtrip in a 2001 Chevy Prism hunk of junk a few years back. Tiny, cramped, uncomfortable seats, smelly interior, shakes over 65 mph, funky brakes, burns oil, a squeaky belt, semi-bald tires, etc. Not at all a luxurious vehicle and I was pretty skeptical about roadtripping with it. Despite all that, it got us where we wanted to go with no fuss. We would spend a few hours in the car, arrive at our destination, then camp for a few days as we hiked and availed ourselves of local amenities, then drive to the next spot, so we really didn't feel like we were in the car all the time.
We still have that car, and depend on it as a single-car family. Still reliably runs like a charm with a bit of love -- shampooing, new tires, a brake job, regular oil changes, and careful driving. The seats we solved with those mesh lumbar support things. We even take it on 5+ hour trips to visit family frequently (around 8-9 times per year) with no issues.
I wouldn't write off the old car completely, but I can also understand the urge to get something newer. If you have to put a significant amount of money into the car to get it in good shape, then that may tip the scales a bit.