Perhaps AirDisplay will work for you after all!
You have a couple of options. They both involve going to System Preferences, Displays, Arrangement, after starting AirDisplay and selecting the iPad in the AirDisplay menu in the status bar.
1. You can simply check "mirror displays". This will give you a copy of the desktop on both your main computer display and iPad. Now, the desktop will resize of 1024x768, and you will get a fuzzy display on your main display (assuming your main display resolution is > 1024x768. Yes, you get a smaller desktop, but you won't have to endure a fuzzy display on the iPad, nor will you need to pan a larger desktop, which is a pain in the butt.
2. You SHOULD be able to move the status bar from one display to the other. But that doesn't seem to work for AirDisplay. I think you are supposed to drag the status bar depiction on the Arrangement window. But you can't select it.
Ah, this seems like a bug. If I open my Macbook (I normally run it closed on an external monitor), I can move the status bar from the external display to the internal Macbook display OR to AirDisplay. But I can't move it with just the external monitor and AirDisplay enabled. Not sure about Macbook/Airdisplay combo as that's not something I'd commonly do.
The dock doesn't go with the status bar. Not sure how to move the dock, but if you can figure that out, you are golden!
(Edit: I figured it out. The dock DOES go with the status bar. However, there is no way to access the dock from AirDisplay, unless you set it to not "disappear". You can, however, use your Bluetooth mouse or built-in trackpad to access the dock.)
You will would have control from the iPad, however.
Basically, what I'm trying to do in this case is to reverse the roles, so that the iPad is the "primary" display and the internal and/or external display(s) "secondary".
But this really isn't what you want to do. Sounds like #1 would work for you though!