I'm all for burgundy - more interesting than brown. http://www.theshoesnobblog.com/2010/06/burgundy-shoes-where-hell-are-they.html
As for pairing the burgundy loafers with your summer wedding outfit, I don't think the colour is a problem. However, you might want to make sure they are dress loafers rather than the more casual ones.
And congratulations on tying the knot!