As a design consultant I would recommend that you use Cisco Access points (1200 series are excellent), with a BlueSocket front end. This will allow them to seamlessly roam between AP’s as well as create a secure connection between client and the network. All wireless communication is basically run thru a VPN type connection. Fully encrypted and secure. The basic model of BlueSocket is the 400, this would support upto around 50 concurrent users encrypted with a maximum throughput of around 30Mbps.
Just my .02 worth.
CiscoCat6k – CCNP/CCDP/CCSE