You could just put in a couple of window units for now.
You might look into split systems. These put the compressor(s) outside, but instead of using ducts, evaporator coil and a blower to get the cool air to the area needed, it uses high pressure line and return to individual blower/evaporator unit(s). These could be moved later on, if desired. Some of them are neat in that you can control the unit with a wireless remote.