First off, you need video editing software no matter what you use, a camcorder (consumer or professional grade) or a dSLR hybrid.
Not sure what all the Windows users are using, but Sony Vegas Pro seems to be the popular choice.
As far as Mac OS X, iMovie is a very decent editor and easy to use. Or you can step up to Final Cut Express or Final Cut Pro (very complex).
As far as camcorder vs dSLR hybrid (e.g. Canon T2i or 7D), it's best to stick with a camcorder.
Unless you are willing to spend money on the actual support rigs, follow focus, loupe (e.g. Zacuto Z-finder), and other accessories, your wife is going to find shooting video with the dSLR very, very difficult.
For an idea of what's involved with video on the dSLR, watch this:
A basic shoulder mount and follow focus will run you around $1200.
I've shot some of my youtube videos on a dSLR (7D and 5D Mark II), but they were very, very basic productions on a static tripod with zero movement of either the subject or the camera.
But if you're willing to risk hybrid dSLR for HD video, then Canon is the only way to go. All Canons record to H.264 natively whereas all Nikons shoot Motion-JPEG (except the recently announced D3100).
To get blown away by what you can do with a Canon 7D (or other Canon dSLR) watch Vincent Laforet's work:
- "The Cabbie"
- Behind the Scenes of "The Cabbie"