Singlespeed gearing for Return on the Jedi

I'm gonna ride my single on Sunday and am looking for a little help selecting my gearing. The expert/pro course looks pretty single friendly with protracted climbs and descents with very little flat stuff. I use a 34x18 or 34x19 here in Santa Cruz, but am wondering if the course is steep enough to warrant a 34x21. Geared riders: Is most of the climbing middle ring? Thanks for any advice. Note: I am old (well over 45) and slow, so nobody needs to worry about me stealing their spot on the podium. Please help me avoid miles of pushing my bike or miles of spinning like a fool.