They can go to Starbucks for Wi-Fi. Or use their 3G cards. Or tether to their BlackBerry devices. Seriously, there's little excuse for keeping an SMB's stuff on-premise, least of all is the threat of some mythical backhoe.
The cloud makes sense when a small or medium sized business CAN'T afford the investment in top-notch reliability, availability, and security for their own in-house infrastructure. With the cloud, that RAS investment is spread across thousands of customers. The likelihood of a backhoe breaking a fiber optic line is lower than some malware or hardware failure deep sixing an in-house server in a typical SMB.
+1 for sure. If you're in a 20 person shop, there's no reason to invest anything beyond the bare minimum into IT, particularly if you're a 501(c)(3)!
Google Apps is free for non-profits. http://www.google.com/apps/intl/en/nonprofit/index.html
You can even use Microsoft Outlook (via Google Apps Sync for MS Outlook) and BlackBerry devices (via Google Connector for BES) if so inclined.
Google Video, part of the Google Apps suite, will take care of your video archives. Get a decent Active Directory or OpenLDAP server set up for authentication. Laptops are the way to go, especially if your folks need to be out in the field meeting with clients or donors. Desktops are irrelevant today except for hardware geeks and fixed function workstations. Don't run your own web server -- you can't scale anywhere as quickly as any hosting company can.
Conclusion: building your own infrastructure makes no sense for your particular operation.