Weaners have probably never been outside before so they'll be scared initially, I would let them have their house and a small area, maybe hurdle or fence off a three metre square for them, so they won't loose their house. After a week I'd give them a larger area and increase it over time. The most I'd allow for 2 weaners would be 1/2 an acre.
Have you thought about sheep, or even renting out the rest of the field for sheep? They keep the fields in good condition and can be rewarding.