For a headless server to simply be able to access, I suggest using logmein or another 'screensharing' vnc type client. Then the system on reboot needs to ensure the screensharing is on or in the automatically loaded via the default user login for the machine.
AirDisplay may actually work, I've tried it for creating a 'secondary monitor', it would require the AirDisplay software to be enabled in startup. But I've never tried using it as the ONLY display for a machine and don't know how it would handle not having another monitor set up. I suspect if you used the display setting for 'mirroring' it may work.
Either option should work and would require it being pre-setup with an external monitor. From my own experience, I suggest looking at a free VNC client (perhaps a lite version) to test how it works. The performance from each software does vary. I've had very good results with LogMeIn and the JaaduVNC that was renamed more recently, these are more expensive than other options. Some of the other options have certain input limitations or may not have been performing quite as well in my testing.
Unfortunately, as each vendor updates their software they all claim increased performance. Doing a 'review' of packages or hearing through someone like me will not give you a 'current' view of what will work best for you. I suggest you try a few lite versions and see if they work well.
My own setup was a MacMini in my basement as a server (which had a screen connected but with the screen turned off). I used remote screensharing with great success, including keyboard command sequences like command-c, command-v. The only thing I don't like about screensharing is drag/drop doesn't work well using the touch interface. If you plan on using the mouse it won't be too much of an issue.
