Microwave vs. Infrared vs. WiFi

I’ve got a little situation that needs an expert’s input.

Can anyone recommend a solution to tie in 2 lan’s in 2 buildings (less than 200 feet apart), clear line of sight on both roofs to each other. Main building has around 50 users. 2nd building about 30. Need to accomplish some type of a voice encapsulation i guess so that the 2nd building can use the existing “intertel” phone system as well as regular data access from main building’s servers/SAN’s

Help someone?