Setting up a lan+internet with
android phone (usb)
pc1 desktop (usb+ethernet+wifi in ap mode)
pc2 laptop (wifi)
pc3 xbmc (ethernet)

pc1 gets internet from android and shares it via cable and wifi to pc3 and pc2.
All pcs will run ubuntu 12.04.

Its sort of working (wifi is erratic) but with dhcp which is not ideal. I'd like to set up static ips for remote desktop, remote control of xbmc etc.

What would be the best way to go about this, while keeping ubuntu vanilla as much as possible?
Will network manager/avahi etc. interfere or do they respect config files?