In the beginning, in the venue search, I despaired. I worried we would never find the right venue. Then we found Irvine and it was amazing. Then...a week before the wedding, the site coordinator mentioned that they were doing construction work in the woods, right over our ceremony site. Since I'm rational, I freaked out and drove out there to insist that we have the ceremony in the woods. She agreed to make it work, and at the rehearsal (after a few stressful days for Mark, who hadn't seen the changes and didn't trust my lack of spacial perception), we decided to use the far corner of the woodsy area as our site - it required a bit of flexibility on our part, and our guests would be in narrower rows than we had planned originally, and nothing was totally symmetrical, but it was still pretty much what we wanted.
But seriously, hold out for what you want. You might feel like you are being pushy or making people's lives difficult, but as long as the weather cooperates, have the wedding you want. Because well, the result is kind of awesome: