Former TSA officer here:
You can bring the iPads in with your carry-on bag, but TSA reserves the right to unpackage them if they find any cause for concern (obviously this isn't an issue if you are not trying to keep them sealed/shrinkwrapped). Most of the time this is due to uncertainty at the x-ray machine. TSA officers are urged to call for inspection if they are uncertain of an x-ray image that could reflect dangerous materials; and lithium ion batteries tend to resemble dangerous materials under x-ray. If you really want to bring them as carry-on, I would pull the boxes out of your luggage and put them in a tray with nothing on top or below them. (don't stack them if you have more than one!!)
If you go this route, also be sure to stay within viewing distance of the iPads, and if at any point an officer asks you to step aside, tell them you do not want to lose track of your belongings. This way another officer will be required to grab your trays (after they pass through x-ray) and keep them where you can see them.
EDIT: if you want to bring them through as carry-on you will almost definately have to break the package seal. Unless you get a very laxed officer, an x-ray image of the iPad in box with the adapter and cable below it will look potentially dangerous to most proactive TSA officers.