Hi xabih,
By Lirc do you mean Flirc?
Flirc + another keyboard (connected via mini-DIN) should work fine.
The easiest way to test if Flirc + [any combination] would work is to use a USB keyboard in place of the Flirc.
If USB keyboard + [any combination] works then Flirc + [any combination] will work
Let me know if I haven't answered the question,
Pleasant regards,
Chris!
(p.s. welcome to the forums)