could you do a quiet time for both of them at the younger one's nap time, by themselves in their rooms? That way your DS2 perhaps wouldn't feel like he was missing out and may still nap? (And, perhaps more importantly, you'd still get some quiet time!).
Or could it be the kind of thing where you may get some resistance to the nap plan at first with your DS2, when DS1 is at home for the holidays, but if you still consistently offer the nap, then after a few times he will accept that he still has to have a nap/quiet time and stop resisting?