I have not ridden the race myself, but I know the area very well and how rugged the terrain is in that part of the world. I've fished and hiked through the area for more than thirty years so I think I can speak with some authority. It's a very remote part of the world as a Google Earth search will show you. A drive into the area will also give you some idea.
The race sounds like an awesome race and I'll get to do it one day. I've only done one mountain bike event, and that was the James Williamson Enduro a month or two ago. It's an awesome event for first timers and experienced riders. The reason I chose that one as my first, was because I had no race experience at all. I wouldn't have been confident racing in the Convict given the number of experienced riders who are drawn to this race.
I'm sure I'm going to get some level of angst levelled at me about saying the following, but I'm going to say it for you and your Dad's sake anyway because you asked what readers think. I hate to be a wet blanket on your Dad's ambitions, and I don't mean to scare you, 'cause you sound like a great person, but I've heard about the number of people who end up in hospital via ambulance or helicopter. I know that could happen from any race, but I think your Dad might want to look for a ride that would not be as taxing and suite his level of experience (or lack of) and skill (or lack of).
If you want to find out more about the race and your concerns for your Dad, I'd also contact the organisers of the event and ask them about it. I can't tell you what they'd say, but I think they'd be happy to talk to you about things and let you know what they think.
I'm not sure where you live, but there are plenty of races around that might suite your Dad better and make you feel better about his racing. Encourage him to get some experience at some other races first, and use the Convict as an incentive to race once he's learned some more about riding and racing.
Here's a link to some races in Australia. You can break your search down into states once you're in.
http://adventurerace.com.au/Search/Mountain-Biking/Australia
There's plenty of races around around, and plenty of websites and magazines all showing lots of races. You have to do some research, as not all the races are listed in the various websites and magazines. Some don't have many dates listed, and others have heaps, so do some digging and I'm sure you'll come up with some races that would be more suitable for your Dad's level of experience and skill level. Fifty k's might be a huge effort for your Dad too, and there are shorter rides around which would be enough to wet your Dad's toes to find out about racing.
I hope that helps you Bobby. Again, I don't want to spoil your Dad's ambitions or alarm you, but I'd be looking to do some other race if I was in the same spot as him.