If you don't say anything at all while standing over two dead bodies, then you're definitely going to jail. In this scenario something along the lines of "these men forced their way into my home, and I defended myself" is a good thing to open with. If they start asking for specifics or you get uncomfortable then tell them you're shaken up, and request to see a paramedic. They can't deny you medical attention and at that point the interview is over.
Know your state laws, and do your best to work within them. If your state has a clear castle doctrine and you acted reasonably, you'll probably be allowed to sleep in your own bed that night.
*I am not a lawyer*
*Edit: Also be sure to identify yourself as a victim in the 911 call. "Two men just broke into my home and/or attacked me and I shot them. Send police and an ambulance."
"And I'm tellin' you son, well it ain't no fun, staring straight down a .44"