Technically speaking from experience over the last 3 years using several Wireless Solutions for VoiP Coverage and Bridges

WDS is the standard for low cost wireless overlapping networks.

The questions are;
How are users going to authenticate? Radius, WEP, WPA, ...etc

The next level up is MESH radios with access, control and management on B channel and data on G

The products we have used are from a largely unknown company called Planet... The U.S. Distributor is www.planetnw.com Speak to Ben. He's a real pro on what you'll need.

The Two channel Mesh equipment is outdoor rated, plus indoor AP are available and a Windows Management Reporting performance tool is included.

Going further up the $$ scale look to N networking. We are about to deploy our first and based on our research with real clients and a large install base, we are going with Meru Networks for a 1 channel autoconfig solution to cover 45 acres and 16 buildings for Data, VoIP and moderate Video Streaming.