US Citizen living in Japan traveling to China on two separate occasions! Help!

I am US citizen currently living in Japan and trying to apply for a Chinese Visa to the mainland. The problem:
I will be going to Hong Kong in March and plan on going day trip to Shenzhen, however later on this year I will be going to Shanghai for a wedding, but I don't know when the wedding is going to be exactly. I am thinking I should get a 12 month-multiply entry L, but I don't have the itinerary for the wedding so I can't book the plane ticket or hotel, meaning I can't attach my itinerary to my application. What should I do? I don't want to have to $130 on two separate occasions.