You might want to see if there is a spinning guild in the area. They may be willing to pay your in-law's/grandparents a fair but lower price for the wool and then resell it for a small profit to support the guild. You might also be able to include in the price of the wool some yarn spun by the guild for you. I would see this as a win, win ,win. Your in-law's/grandparents get some money for something they have been trowing away, the guild could get some wool for training new spinners of to make some money to support the guild, and you could get some home spun.