Not once in a lifetime, you'll be back. First time. My recommendation is either go early, stroll the line of bikes at the staging area, do not drool on the bikes and then go to parade start and watch em roll by. I can't explain how moving the sight and sound is especially last year with all the progress. Or .....
Find someone to ride with and go for it. You're the first people in the parade so at the end presumably you just get off the bike. Profound thanks for the ride and walk backwards to see it all.
The parade is kind of a mobile experience, you find a good spot, stand and watch, see someone you know or a group you're involved in and pop in and walk for a while. Step out and walk backwards or forwards. .... Or you can just stay put. Keep in mind the side of Market you are on determines if you'll freeze in shade or boil in sun. think layers.
As for a motorbike tour I think you should head south out of San Francisco to Half Moon Bay perhaps taking 92 up over the hill. stop for a break in Half Moon Bay, keep going down the coastal highway to here for lunch at Duarte's perhaps
http://www.pescadero-california.com
You could continue to Santa Cruz. the boardwalk's fun but more important there are redwoods to hug.