Hi,
if you mainly use a keyboard for backing tracks for your piano playing, couldn't you put your keyboard next to you rather than on top of the piano, might be more of a visual issue with him rather than anything against keyboards.

Could you put your backing tracks on a laptop as audio files?

For the songs that you do play the keyboard, feature it as an instrument in it's own right, ( instead of an add on to the piano) feature it the same as you would guitar playing or the piano?

Could be worth finding out if the issue is the keyboard itself , OR the fact that it sits on top of the piano.

( hubby would have throttled me if I'd sat something on top of the baby grand , except for the silver candelabra. ( seriously he bought a candelabra for it. Haha )

For me as an audience member, be a case of wow, this guy plays 3 instruments and sings.