My biggest fear is them wanting to blow one of these photos up and it just be so horribly grainy and not sharp. Any suggestions would be awesome. I am going to walk away from editing for awhile before I jump off a cliff.....
I looked at the largest version of the image that is available on Flickr (both the original and the sharpened), and it doesn't really look too bad. I would make a 100% crop of one of them to show what I'm looking at, but I'm guessing that's considered "editing" so I'll hold off. I'm looking at certain things like the crispness of the outline of the man's tux, the detail in the flowers, etc, etc... it
really doesn't look too bad. So, I'm not really sure how much sharper you want it to be...
Also, looking at a 100% crop of the sharpened version of the photo, it seems like you've sharpened the noise a bit. As a result, the original version actually looks a bit better to me at 100%.
It seems like what is really bothering you is the noise. As others have mentioned, the 5D Mark II is a great camera with good high-ISO capabilities. But the fact of the matter is that ISO 2500 is
still ISO 2500,
no matter what camera you're using. Sure, using ISO 2500 on a 5D Mark II will produce a
much better picture than using ISO 2500 on a Rebel T1i. Nonetheless, the fact remains that using ISO 2500 on a 5D Mark II will
definitely produce a noisier photograph than using, say, ISO 200 on a 5D Mark II. There's really no way of getting around that fact.
Given the high-ISO you've used, though, I really don't think that the noise level in this photograph is nearly as bad as you seem to think. Nor do I think that the sharpness is nearly as bad as you think. That's just my two cents after seeing the 1067x1600 versions on Flickr.