If you won't be serving it until winter and you won't be refrigerating the keg, then it would make sense to prime it with some sugar to cut down on oxidation. Add sugar and enough pressure to seal the keg and check it occasionally for carbonation. The fermentation will scavenge the O2 while it carbonates.
I could be wrong, but do you really need to add sugar to cut down on oxidation. If you rack to the keg then purge w/ CO2 then there shouldn't be any worries regarding oxidation right? I just put a winter warmer in a keg to age for the first time and did it this way w/out any sugar. I'll put it in the fridge and force carb in December.
It's because it is hard to get all the O2 out of the keg, but the yeast eating the sugar will consume it. Ever notice that bottle-conditioned beers stay fresh longer than counter-pressure filled bottles? Even though I don't ever leave kegs sitting around for any long periods of time, I thought this was a good idea to circumvent staling.
Amen to refermentation for long-lived brews!