Airplay tab is missing

Question

with apple product everything is always easy, right?
dear all, then i really need help and i am sure you are able to solve the issue.
here is the challenge to solve:
network is right installed on appletv and computers, firmware update on all machines is done - all is on and reset - tv also is on and connected.
the airplay icon apears in itunes it self and i can play music via appletv on the large screen as it is supposed to do.
same works with the iphone - here i even can browse the pictures.
so far so good!
but there is no airplay tab in "displays" nor in the "menu bar" showing on my macs (details below).
i also would like to use the appletv for keynotes - pictures - documents....
but the airplay tab wouldnt appear - as often as i tried and checked.
shame on me if there is a simple solution - hundred stars for the one who can solve it.
i am checking dozens of comunities etc and hours already today to get a hint to solve that - nothing offers a solution within my ablilities to solve the issue.
appletv 3rdgen sn
CO7JWOLMDRHN
imac with sn
C02HM0HBDHJW osx 10.7.5 build 11G63
same problem with the macbookpro sn
C02HK1F7DV11 osx 10.7.5 build 11G63
we run a apple mini server system on the same network.
we run it in beijing - china.
the game is on
thanks
arnd

Answer 1

this helped my question - fast!
i just would have loved the answer when asked if i can use the appletv system with my setup at the apple flagship store in beijing -  here i just got the answer :"sure. easy." and of course understandably for government reasons that is a fact in china: "but we cant sell it in the shop due to licensing issues here in our shop". 
they know very well our purchases as i am unfortunately more often than necessary there with lots off harddisc failures (3 out of 12 within ~2 years), screen issues (faulty screen pixels right from the first day at the first imac24.5" we bought - did not even get a replacement one but needed to wait 3 weeks for repair , dust stains) mouse trackball failures and others.
i see -  now i need to either update my imac and macbook pro with mountain lion, or leave it. but what is even worse, only a minor group of our clients will be able to use the wireless converence system because they rarely have the latest mountain lion as well, and for them we installed the machine.
but to be fair - its my problem not to have gone through all tems on the webpage but trasted the genius at the service counter. what a world. shame on me.
by the way if you are interested:
do you have any idea what this pixel graphic issue could be on my mac book pro. it occures frequent, randomly after sleep periods and can not be forced to appear for demo issues. the screen first is black- nothing at all if i move the mouse pixels get visible as if i used a sponge to clean a dusty table. sometimes a complete square changes as well. once i cleaned long enough i find the insert window for the password and here we go as if nothing happened.
the issue appeared after the harddisk of my second last macbook pro broke just a couple of month old (4 or so) in jan 2012 (again get only a repair not completely replacement (took waiting time of 2 weeks and all the hussle to set up the temporary replacement on and later back - all our mac purchases are bought with extended apple care warranties btw).
when i finally got again problems with the harddisk and wifi connection the flagship store replaced the macbook in december 2012. brand new - mirrord system but after a couple of sleep modes the pixelgraphic appeared again.
no one at apple can help me - even the guys in brussels who were verysupportive could not give an answer. at that very same day though on the counter a client next to me came and had just the same problem.
i dont know what it is and what its caused from - but i had a couple of very unpleasant comments when some clients saw the problem at a presentation.
cheers
arnd