Well, that depends, how close everything is going to be together.
If things are close I'd recomend getting a router and connecting the pc's and the xbox to the router.
If you need to go wireless it depends on what you want to do.
I'd recomend atleast trying to keep the xbox wired, as the wireless adapter for the xbox is pretty pricey.
Do you need high speed transfer between pc's
Many questions can be asked, so more info would help