I would choose option 1 if you want to make sure you receive the background check in time. I think they'll return your application if all the documents aren't included.
To make your FBI request go faster, you could send them a prepaid courier envelope to return your background check. It will save you a few days. I suggest you send them a USPS Express Mail envelope with enough stamps to cover postage. Second, pay the $18 fee by credit card (there's a form for this on the FBI website). And finally, make sure you put your deadline on both the outside of the mailing envelope and your application.