Type of visa to get and where can we apply for visa?

We are planning a trip to China next year to attend a banquet to celebrate of my son's marriage to a Chinese citizen in the town of Xiushui in Jiujiang. I'm not sure if we should apply for the Q2 or L type. We know we will need an invitation letter from my son's wife's parents. We plan to sight see as a tourist for the majority of the time and also go to Hong Kong. Since visas are good for 10 years now, we see ourselves returning in future years for mainly sight seeing purposes. On the other hand, my son will likely be accompanying his wife to visit her family as well. So do we get a L type with the invitation letter and my son needs a Q2 with the invitation letter, or do we all need Q2? If we return in future years will we need a new invitation letter or is it only required when applying? Also we live in CO and understand that the embassy we're supposed to apply for the visa is in Chicago. My other son who will also be traveling with us lives in CA. Can my son in CA submit our applications in SF for us since it is more convenient for him than for us to go to Chicago?