"(via volume control)"? Which volume control? Something on the receiver? TV? In-wall control?

How would one switch the kitchen source "without any extra remote commands"? Are you proposing an in-wall line level selector switch in the kitchen?

One scheme would be to include an amplifier for the kitchen, selector switch, and an Audioengine attached to the TV's headphone output -- assuming that the headphone output exists and that it mutes the TV's speakers. Another scheme is using the stereo analog output from the cable box with the Audioengine -- but this would not include Apple TV and Blue-ray.

A concern in any case would be handling of the TV's audio output while watching a TV "App".

In my opinion, the "without any extra remote commands" makes this more difficult than it needs to be. Will you be using a unified remote, such as a URC, RTI, Logitech, etc.?