Can you check with your Mother In Law about vaccinations?
Have the sheep moved to you? If you already have them on your land then I would get an egg count done and worm accordingly. It doesn't sound like you already have sheep to worry about bio security.
Do you just have the 12 acres? If so you might want to consider splitting it into smaller paddocks for future management of the sheep and your pasture.
What breed is your little flock?