New to the forum so I hope this is the right place.

I am in the process of building a local community website for my local area in Scotland (East Lothian).

"Our business will be a on-line local community website based in East Lothian. It is a not-for-profit, business with the aim of bringing East Lothian closer together through high quality community news, discussions/debates, videos, directories, social networking and interactive content. We will use existing “Web 2.0” technologies such as YouTube, Podcasts, Blogging (Twitter), making sure that the website is easy for all our users (which will age from teenagers to the retired) to access. The ability for the site to seamlessly communicate with other sites such as Facebook, Bebo, MySpace"

I am at the stage where I need to choose a platform to build on: the following crieta should be met:
open source , extenibilty, cost, time to develop/extend and ability to publish content easily.

Some things that will be included on the site:
Local News stories (updated daily/every 2 days)
Information pages (eg history of East Lothian, local clubs and orgs)
Business Directory
Embed YouTube Videos,
Feature Articles (once a week/fortnight)
Online Debate Forum (locals can discuss relevant issues)
Review Section- review restaurants etc.

I've look through a few projects and have narrowed it down to two contenders- Joomla and WordPress.

Any advice or ideas (PS we cant develop on MS technologies)?