network with 2x airport Extreme, airport express, and macbook

I have:

Macbook ( not N capable)(running latest airport utility on snow leopard)
Airport Extreme (dual band)
Airport Extreme (N wireless)
Airport express (N wireless)
xbox and DVR connected via ethernet to N wireless extreme.
moto airboard cable modem. (non wireless)

So, here is the scenario.

Dual band upstairs hooked up to Cable modem. Functions as the only wireless access point.

N wireless extreme downstairs has xbox360 and DTV dvr connected via ethernet, and the extreme itsself needs to connect to the dual band wirelessly.

Airport express has stereo hooked up for airtunes.

How should I have my network configured for this to perform properly?

Since the macbook is not N wireless capable, I figured that having the dual band as the only station accepting wireless connections would leave everything else on the network to interact on the N band.

The extreme downstairs needs to somehow just connect to the dual band via N band, and not accept any Non-N wireless connections, since it is not a dual band unit.

My biggest issue is that currently nothing keeps connection for long... I am having to reset everything after a day just to get the dual band to see the internet.

Obviously it is very important that I get this back running soon, without streaming netflix and hulu I am a shell of a man.. So I will offer a generous $10 via paypal to the first person to give me the appropriate settings for all my gizmos.


Thanks in advance!

Essentially I am just wanting to turn my older N wireless Airport Extreme into an ethernet hub, and connect it to my network via the N band on my new Dual Band AE...

This can't be that difficult...