Like Terry says, a 12" rough-in toilet like the Toto Drake II will fit happily on a 14" rough-in. You will just have more space between toilet and wall. The 14" Unifit will move the toilet 2" closer to the wall, eliminating the gap between toilet and wall and making it not protrude as far forward into the room, but you need a toilet that works with the Unifit, like the Vespin II that Terry recommended.
If you want to see how much more work it is, here are the instructions from Toto. Really, what you do is drill a couple of holes in the floor, using a template provided with the toilet, and secure the Unifit to the floor using those holes. At the other end of the Unifit, you mount it to the flange using a wax ring, kind of the same way you would a toilet. You then put the toilet down on top of the Unifit, plugging the outlet of the toilet into the Unifit, and secure the toilet to the Unifit. If your husband is comfortable using a drill into flooring, it's not that big a deal. But he has to be the kind of person that doesn't mind putting on the glasses and reading directions and who doesn't mind measuring carefully. The 12" Drake II that I mentioned is a more-traditional installation, just mounting onto the flange.
With a two-piece toilet, I believe that you can put the bowl in place before attaching the tank if that's easier (because it's lighter and easier to maneuver).
The couple of things to think about: does the water supply come out of the wall or out of the floor, and where does it come out? The toilets that use the Unifit have a "skirt" on them, and require a little more distance from the centerline for the water supply at the wall, but not as much as Toto recommends. We have some easy-ish ways around that if your husband needs help.
Let us know how it goes. We like seeing results!