Well, they'll be easy enough to catch, as they're used to coming to you for food? So if you put them out and they can't cope with the stroppy ewe, you can get them back again easily enough!
Ideally they wouldn't have 14 acres of lush grass, no. I'd certainly give them a good (chelated) mineral drench before turfing them out onto that. You'll still be giving them cake, though?