Bootcamp is the only way to do it. It's essentially a windows partition. You boot into windows. Parallels and Fusion are cool, but they don't really provide the stability and low latency to use a DAW. I've tried running Sonar in those, but it doesn't work very well at all. To track in Sonar you'll need to use Bootcamp for sure.
Another option: I record 48 tracks each weekend in Sonar on my live setup and then import the audio into logic on my production machine. You could do the same thing: Record in Reaper on your air - then transfer the audio to your other machine in Sonar. It's a little cumbersome, but it's a quick way to get it done if you don't have time to work on your computer, install windows, run updates, etc. That's the part that drove me crazy with bootcamp. Sitting and waiting on my computer drives me crazy.