If he didn't have a demanding job a wee nipper and was looking into running this at a competitive level then yeah core strength and cross training is an excellent way of getting the most out of your body. It sounds to me like its a bit of a fun run for himself,supporting the various charitys associated with this event. Last years event was in septemeber,so to make it round enjoyable if i was in his position i'd concentrate whatever spare time i had into actually putting the miles in rather then,situps,skipping etc.
I agree any excercise can't hurt(providing you do it safely and properly).
On paper it looks a very good event too,sizable crowd from elite to fun runner and walkers too.

Rob