JOEL - To Mormons (not Mormans) the temple is the most sacred of all buldings on the face of the earth. Because of this, admitance to the temple is allowed only to active members of Church of Jesus Christ of Latter-day Saints. They must hold a valid current temple recommend that they have obtained from their Bishop, after correctly answering several questions relating to their obedience to the Gospel principles and commandments of God. I assume the groom's parents were not members of the Church and/or did not hold current temple recommends. Therefore, they were not allowed into the ceremony. Also, the actual marriage ceremony is held in a small room that has an altar in the middle where the couple kneel while they are married. The room can only hold a few people at a time and so they limit the number of guests to close family members and perhaps a few friends who have temple recommends.

It is incredible how many untrue rumors and ideas seem to be communicated among those outside of the LDS Church. There are several about what goes on inside our temples. Couples are NOT married in the nude. In fact they have on more clothing in the temple, covering them from head to toe, than what they would normally wear outside the temple. The women even wear a veil that covers their faces. Marriage vows made in the temple seal a couple for "time and all eternity", not just "until death do you part". It is a sacred three-way relationship that is made between the man the woman and Jesus Christ. More information about temple marriages can be found at this site.
See also: http://www.mormonhaven.com/malia.htm

I am not sure why your friend would need to be "secretive" about his religion. Since he is new in the church he may just feel somewhat insecure about answering your questions. If you are talking about matters relating to the temple, we are instructed not to talk about those things outside the temple; not because there is anything wierd or unnatural about them, but because of their sacred nature.
You said "they were getting married that evening at another church with family and friends present". The only place where they would actually be married is in the temple. Often times couples will have a small ceremony during a dinner party latter in the day at the local Mormon church building (different from a temple) where they exchange their rings. This is often done for couples who have relatives and friends who are not members of the church.