I am looking to add wireless capability to a fixed wired network with 20 desktop computers to enable secure wireless VPN access to the LAN as well as internet access from employees' personal laptops/ tablets. usage would be no more than seven total, rarely more than one at any one time, and virtually never more than 3. The current network is a single LAN and single WAN using a cable business IP gateway and Sonicwall TZ105 router and multiple switches. The building is very large, built in the 1890's located on four floors with plaster walls and ceilings