Another option that would work for WorldWideWarren, instead of MBP you could take along an Aiport Express - I have the May/June 2012 release $75 Apple refurb - set up with a local network, fire it up, then join the network with ATV and iPhone. Anything that has the airshare symbol will stream to the ATV.
I set up the Airport Express wirelessly by opening airport utility, select the Express, edit, then
Wireless>Newtork Mode: Create a Network
Name: b
Security: I used WPA/WPA2 Personal
Password: your choice but it must be 8 characters
Then
Internet> Connect Using: Static and the IPv4 address filled in automatically, for me a 169. address
Router Address: I copied the IPv4 address but changed the last 3 digets to 254
Then update
Two errors will come up:
No DNS Server
Ethernet Unplugged
I was able to select ignore and now they have green dots by them.
When you connect to your AppleTV you will need to select the network name you created, enter your password, if selected, then a screen comes up saying "Connection Failed" Just select "Continue Without Internet" Then the Configure IP window comes up next. Select Automatic.
Apple TV will apply the settings and the WI-FI Configuration window will show up. Just click your menu button on your remote, go back to your idevice or computer, then start streaming to AppleTV.
The nice thing is that it works with everything. Currently I have a Mavericks and Lion OS computers connected, as well as my iPhone 5s and iPad 1. I can play movies from my iPad or iPhone 5s to AppleTV using the airplay. Powerpoints via AipPlay from Mavericks and Air Parrot from my Lion computer.
Problems: When I selected wireless options and selecte 5GHz Network>Save>Update a Invalid value warning came up. When I clicked>Review Settings I saw the IPv4 address had changed to an address beginning with 192. which is the same as the wired network in our building so I just> Cancel > Don't Update - cancelled out of the Update. I suppose, if you really needed a 5GHz network, you could just copy the IPv4 address down to the router line, chaning the last 3 digets or try copying the Router Address up to the IPv4 line and change the last 3 digets, ok, just the last diget would suffice. But mine is working so I am leaving it alone.
What I cannot figure out is how the Airport Express stayed connected to my Mavericks computer as I changed the network. To start, the express and iMac were both on network a which has the 192 addresses, once I changed the wireless name to b and the Network to Static with the 169 addresses I figured it would disconnect, but it did not.
Something else I have noticed (not being someone who works in setting up networks) is that if you connect wirelessly to a computer connected to the internet or LAN, the IPV4 address will also change. Doesn't seem to disrupt any other connections.