I admit that I dont play around with apple products nearly enough- hence my stupidity regarding these questions:

1) Can Multiple airport express's be used together in the same household while allowing any family member access via their iphone or ipad?

2) Is it possible to multi-stream one itunes account using individual Airport express's for different zones?

3) If you cannot multi-stream, will the mutliple zones with each their own airport express all be synced up properly with no delay in the music when listening to the single stream of itunes? Like Sonos.

I basically am asking if these will operate the same as the Sonos systems that we typically set up and install. Customer already has them installed and loves them and says they do the same as the Sonos. I'm not saying they don't because I dont really know. Thanks.

Multi-streaming is only possible through a computer and iTunes. Airplay via iphone, ipod and ipad is not possible as far as I know.

Ok - that makes sense to me. What about the syncing? If i have 3 zones all with their own amplifier and airport express and i am playing a song from itunes into those three areas together - are the areas synced up or are there delays of any sort?

I don't believe multi streaming is possible at all, whether from a computer, or an iDevice, unless something has changed recently.

As for the delay, I am not sure.

I can't speak to multi-streaming but I do stream Pandora to my Apple TV from my iPhone and it works great.  I have the output going to my multiroom system and surround receiver Only has optical or HDMI out so you may need a D to A.  Check out an app called Airfoil

you can multi stream from iTunes on a computer using airplay.
from one iTunes to multiple zones in sync. you can even control the volume of each zone from AirTunes.

you can also download software on mac (and pc?) called airfoil that lets you stream anything over airplay (beyond iTunes) and with finer grain control.

on iOS devices (sans verizon till iOS 5 i believe) you can stream any content on your device (pandora, spotify, etc) to one airplay zone at a time.
multiple iOS devices can stream to different single zones at the same time for different audio streams.

I'm sure in the future you will be able to do multi stream directly from the airplay device...but for now you can't.

When I think multi stream, I think of different music to different airports. You can't do that from a single instance of iTunes, can you?

no but you can do it from multiple iTunes machines ...
and from one iTunes you can stream to multiple airport express's