I'm going to veto the Haidian idea for selfish reasons--if today is any indication, I'm likely not going to be feeling well enough to travel over there, and I'm not a QuanJuDe fan at all. So let's confirm:
Sunday October 9. Line 10 Option 1, start 6 pm with drinks at Enoterra, Nali Patio rooftop. For duck dinner option, I'm leaning towards Dadong over Duck de Chine as it will be a little cheaper and I grump at DDC's automatic 10% service charge. But it is a slightly longer walk from drinks to Dadong than to DDC.
I want to present some additional non-duck and non-Chinese options in the general vicinity. Let me canvas a few places--partly to jog my memory and partly to see if they are still there. In Beijing, anything could have disappeared in my 4 months' absence.

I'll be back on this thread in a few hours with additional possibilities.
trueblu, if you are reading, please check in. I know you said you had a Sunday meeting. Will you be able to join us for at least part of the time?