Form i-130 got approved. Form i-864 and i-864a help!

[otasi]

Thank you for your answers.

My wife (USC - petitioning for out of state immigrant parents) just got a letter that their i-130 forms was approved. I understand that we now have to wait for a correspondence to contact her parents in Vietnam before we have to fill out form DS-261 and DS-260.

I know we have to file the Affidavit of Support form i-864. My wife does have a job, but my she does not meet the required poverty guidelines for herself and both her parents combined. I, on the other hand can meet the requirement of supporting a household of 4 (My Wife, Myself, and both her parents).

1. Our question is what are our options on what to file for the Affidavit of Support. Do we both file i-864, and then myself file an additional i-864A?

2. Our second question is instead of having my wife and I be co-sponsors. Should she just let me be the only sponsor, or is that even possible?

Here's a run down:

My Wife (USC petitioning for immigrant parents) file i-864 as joint sponsor
Myself (USC spouse of petitioner) file i-864 as joint sponsor and i-864A as supporting household member

or if possible:

Myself (USC spouse of petitioner) File i-864 as the sole sponsor? If so do I still need to file i-864A?

Thanks again for looking.