What should I be doing a week before a long distance bike ride?
The correct answer is both. You should do a long ride, around 80% of your goal distance 4 days before your actual ride, and then rest off the bike for 3 days. 

That gives your body a wake up call that serious exercise is coming, and then a rest period to build up for it. 

This answer has some explanation about why, but the only real debate is in the timing of the ride and the length of the rest period.

For most people, 3 days is enough to recover, but not so much as to lose the gains you made. 

FWIW, 50 miles is a long ride, but not so long as to need to be excessively concerned with your training schedule, as long as you've been putting miles on the bike, and as long as you pay attention to eating the right food, in enough quantity, both in preparation for the ride, and while doing it.