Can Apple TV handle multiple devices

Basically AppleTV can only perform Home Sharing with one account, but if you have several computers setup for itunes using that account, they can all stream to AppleTV.

So for example, I have Macbook, Mac mini, MacPro each with slightly different libraries in iTunes all registered to the same iTunes ID, and each computer is accessible separately in the AppleTV menus.

Similarly any iDevices you have set up for home sharing with that account can use AppleTv as an Airport output destination, or alternatively you can use the remote app on any iDevice to control any registered local itunes library - you can either stream from the iDevice to AppleTV or control a computer setup for use by the iDevice's remote app.

This will work fine for a TV connected to AppleTV 2 via HDMI - whether or not it will distribute to the B&O system over HDMI I do not know, but it probably will if it's HDMI and HDCP compliant.

You will not however be able to watch different things in different rooms from one AppleTV 2.

You don't select the remote controlling iDevice at the AppleTV though you can select computer for streaming using the IR remote.

I've not done major testing but just started a TV programme playing on AppleTV from itunes.

If I then go to the remote app on my iphone it shows what's playing now. The iphone remote app allowed me to change what was playing from that itunes library, so in theory one user can change what another has started watching.

Any remote that is capable of controlling the Apple TV will be able to control it at any time, so yes if you start something, someone with another remote can change things. Devices such as the computers that can otherwise stream content to the Apple TV cannot interior something that is being played already.

iOS devices using AirPlay can interior content being played on the Apple TV but computers can't.

Interrupt

If e.g two people both with iOS devices both try to AirPlay content to the same Apple TV the last person to send content will interrupt the stream of the first person, and a steaming fight can soon break out with both people very quickly! You could if you want to turn off AirPlay and then this forces the household to use the remote control to choose what you want to stream from iTunes, but obviously this loses functionality. Perhaps the solution is to buy more than one Apple TV then your daughter can have her own Apple TV in her bedroom to stream to (assuming she has an HD ready TV in her room).

Hope that helps.

One solution to your dilemma, would be to set a temporary password while playing content, that would require anyone trying to stream content by AirPlay to enter that password until you remove the password.