Not sure how much experience you have, but these are my tips, use what you want:
I would not get the full 50 head all at once. You will have a new set up, and while one always thinks it is predator proof, sometimes you learn the hard way that it is not. Another consideration is with getting all 50 birds at one time, is that you have 50 head of pullets, then two years later 50 (- losses) of old birds. Personally I like a multigenerational flock, so I think I would get maybe 25-30 this year, then add to the flock next year.
I tend to think of free ranging as more as a fringe benefit for me and the chickens. Mine do love to get out and peck, it will reduce my feed bill in June and July, but after that, there just is not enough bugs available and I live on a ranch. So while people envision them getting out and foraging their feed, they will still need a lot of feed. The more space you have, the more predators you also have, the dogs might work well, but then again, maybe not.
In the winter, free ranging is strictly limited by the day length. You can use free ranging to cheat in the summer time with your numbers as the days are so long, but with winter, you need to make sure that your flock will live inside your set up, as they are on the roost for 14 hours at a time.