Ugh, I feel for you. I'd be stressed as hell, too.

How fancy are the folks wanting this shindig to be? Could you get away with handmaking some of the decorations/items? For my wedding we printed our own wedding invitations and being total novices at the time, they turned out really well. You could also handmake table decorations and rice/grain/whatever is eco-friendly and popular now bags for after the ceremony. Of course, that stuff takes time but if you get started now you could potentially pull it off. It also depends on how much free time you have, as well.

Don't give up hope, everything will work out one way or another.