Some people age more gracefully than others. My mom is a better driver at 81 than most who are much younger. Annual testing is probably the best way to insure age hasn't hampered one's ability to drive. Driving and texting is the bigger problem.
It's a special thing you are doing for your Dad. Ditto on repairing what's needed and have some fun with it. Painted surfaces with patina have a lot more character than a new paint job.
Sorry about the car troubles. It looks like great fun!!! My wife and I want to visit New Zealand. Maybe we should plan it around your next event. I don't think I will bring my car though...my steering wheel is on the "wrong" side. When is the best time of year to visit and when are your events...