You should break you're training up into 3rd's. first third being base, 2nd third being speed, and the last third being the actual ride.
Start off with you're base km's.
try to get in around 200 - 300km's a week.(Slow rides)
Gradually build up the number of km's from 30km a day to 100km, and one 160km day (sunday's easiest).
Don't go out and do 160km's in the first few weeks every day, just once a week.
The second third, should be dropping off the km's, but raising the intensity. so say 300km's a week at a moderate heart rate eg. 135/140 beats per minute.
Gradually build up the intensity until it is the intensity of that of the ride he is going on.
The third stage is doing the ride. Number 1 rule, is pacing yourself. Keep at a pace that you know you can finish the ride in. Don't kill yourself in the first 2 hours, because you'll be kicking yourself about it later. (a huge waste of energy you could use to keep yourself going, rather than dieing halfway)
Personally i enjoy GU Energy Gel's, available at all good sports stores (amart, rebel.. those sort of places)
Another good snack is a banana, milo bars, nutri grain bars, and uncle toby's yoghurt tops bars..
basically any bar that you can easily swallow. Get you're father to try different bars and different foods out while he's training. that way he knows the foods that he cant eat while riding, and the one's that go down well.
Finally.. HAVE FUN!.. Enjoy it.