Oh, sorry everyone. Actually THAT wedding isn't until next Saturday (the 13th) and I am in the middle of another one right now so I haven't been around to reply.
I did some experimenting and came up with something pretty good. I used many of the ideas and tips you all gave. I did several tests and the one that was the best was to make a bechemel, infusing the milk with a bit of nutmeg, cloves, peppercorns, a bay leaf and tarragon. After straining, I added some grainy dijon and horseradish and mixed it into the roux. When it was thickened, I adjusted the seasonings with a bit more mustard, kosher salt, fresh ground black pepper and a splash of worchestershire. I served it with a ham coldplate to my guys that night and it was a big hit.
Sorry I don't have quanities, if anyone wants them I can figure it out for you. I was making a small amount for testing and will be making about 3 - 4 cups for the event!
I will report back on how it went over for sure. Thanks again for everyone's input.