I think getting the car down there is absolutely worth it.
My nephew did the program without a car, and boy you really have to spend a lot of time getting places with the shuttle. Disney would sometimes give him and late shift followed by an early morning shift (college students get lots of the shifts no one else wants -- slave labor for Disney lol) and with the shuttles, etc. when that happened he'd only get maybe 5 hours of sleep to be able to get home, sleep a little, get ready, and get back with waiting for shuttles and all the time the shuttles take. You do what you have to do, and it's still, of course, a great experience. But gosh, if you son/daughter has a car it would be so nice for them to have it down there. I know my son who is in college right now is thinking about maybe applying and doing the program if he would be accepted, and as much of a pain it would be more me to do the drive and use vacation days for that (I have lots of SW points and always fly down direct for free in 2 1/2 hours), I know I would do it in a heart beat for him to have that convenience. The freedom and flexibility of a car in Orlando makes all the difference. I don't even like to be in Orlando for a week on vacation without one lol. // Like you, I wouldn't want my son to do the drive alone, and would do the drive with him on both ends.