well my uncle whos very religious was once asked this question about marraiges in muharram and in reply he related that hazrat imam hussain himself conducted the nikkah of a man and woman from his kafila on the 7th or 8th of muharram, now i do not have any refernce for this so if this info is wrong then im sorry in advance but it does totally make sens... he went on to say that things that are haraam are haraam all the year around and shouldnt be done in any month, weddings are a sacred institution and if conducted properly it could be done any day of the year... and i so totally agree!
I second that. The reason why some people avoid having their marriage in the month of Muharram is due to the rasmein they carry out. Most of them are haram, (loud music, dancing, mingling with the opposite gender etc...) So people try to avoid it in the "Holy months", and decide to play the role of a proper muslim during that period of time.
It's just like Ramadan...Everyone goes to the masjid and prays. However, as soon as it's over, the masjids are empty again; families don't eat togather and the distance grows once again until next year!
Khayr mate, it's said there's always khayr in mashwara. Allah will do you good since you have good intention.