The INS person really gave my parents\' hard time because I bought 8mons round trip tickets for them. They had to wait for extra 2hours at the custom before they were let go. Also, my nanny had to buy a return ticket for her sister at the airport(her sister came with a one way ticket) to show the INS and only after that her sister was able to enter the US. So my suggestion is buy tickets that can be changed with a charge. And change the return date once they are in the US. Good luck:)
