Bring money from South America to the US.?

If they don't have one now, it would make sense for your grand parents to open an account in a local bank and the buyer/s can deposit the payments directly to that account. That way they can transfer the money to a US bank and never have to handle it. Hence, no muggings or killings. If they transfer the money in amounts of ten thousand $ or less all they will have to pay are the bank fees.