Hello!

I am looking to do a three cam shoot for weddings that include the Panasonic GH2, Panasonic AG AF-100, and a Canon 60d/7d/5dii (one of the Canons).

How well would the Panny footage match the Canon's? I've seen comparison footage and the color profiles/saturation, not to mention resolution and sharpness, etc, seem very different for the same scene. How hard is it to match these three cameras together in post?

I don't know how they will match in post but I will tell you you want to match them as close as possible before the shoot. It's a lot easier to do little tweaks in post than to take big swings because the probability of matching that would be slim and none.
The best thing to do is to use as many of the same type (manufacturer and model) of camera as possible but since that doesn't appear to be possible, get all the cameras together and get them set as close as possible to one another. Whatever is going to be you A or primary camera, use that as the basis for matching the other to that if you can but at least try to get them as close as possible otherwise you could spend many hour in post trying to match and be very unhappy with the results.
YMMV!

Right, of course correction in post is harder, but I'm wondering if anyone has successfully done it with the Pannys and the Canon.

How would you match in camera btw?

You should get the cameras in ADVANCE and do some test shots. That's the only way you'll have a realistic comparison...

While it's possible to intermix, it's usually a bit of a PITA, and you'll still have some differences in "look", which may or may not be noticeable to the casual observer/viewer.

As Don says, the closer they are when shot, the easier your CC in edit will be, and this is why just using identical cameras is where most everyone ends up...