If you are planning on getting married than I say go for it! This is a trip of a lifetime. And I agree Venice has a smell, it's even more so in the summer than the winter time, but it's not as bad as some say...at least not for me!
Also, about having a man be your maid of honor or a woman be the grooms best man. This has been done several times. In fact most brides have a guy that is there best friend and most grooms have a girl that is there best friend. So, if your best friend is a man and you want him to be your maid of honor, than I say go for it.