I went to a wedding this past fall and they had pumpinks that were painted ivory/white. I later saw these same pumpins at Michael's (craft store). As for the silks, I got all the flowers and rose pettles to do my wedding for $30 (but i'm also only doing mine... but then again also got roses, not sunflowers or something of the like) they look really goregeous and they will be something that I can keep for the rest of my life (todays silks aren't the silks of our grandmothers). If you think you can grow them by all means go for it, just remember that you probably don't want to be cutting down flowers and putting them together the day before or the day of your wedding, you are going to have enough to do already.

Best of luck in whatever you decide! :-)