I am currently on the local advisory board of Center for Inquiry Portland, and was also among many who attended a training in Portland just last month to become the first "Secular Celebrants" here in the Northwest for CFI.
As you may have already discovered, anyone can "officiate" a marriage ceremony, but shockingly, in all 50 states it is illegal for an atheist to "solemnize" a marriage. To sign a marriage license, you must either be a civil servant or be ordained by a religious organization (recently in Florida they've added notary republics to this short list). To get around this law, most officiants get ordained through the Universal Life Church, an online diploma mill. We at CFI take the principled view that this law is discriminatory against non-believers and believe that the law needs to be changed. (If my son wants to grow up to officiate weddings for a living, he should not have to associate himself with a religious organization to do so.)
It's a very exciting time to be an atheist! How would you like to be the first wedding in Oregon (in the Northwest) to help set us up for challenging the law? Until the law is changed, CFI's Secular Celebrants cannot solemnize a marriage - we can only perform the ceremony - so we still need a legal authority to actually sign the license. But, using secular celebrants will set a precedent to gear us up for challenging the law.
Well, I suppose that's true, an atheist can solemnize a marriage if they're also a civil servant! But you can't sign a marriage license as an atheist "officiant" otherwise. It is shocking, isn't it? I had no idea myself.
I had a minister perform my marriage ceremony (a looong time ago). He was my foster father so it was a sentimental decision. I wrote a secular ceremony with the traditional readings, songs, candle lighting.... I even kept in a "moment of silence" so that if people did want to pray for us they could. I don't know if many people even realized that there was no mention of anything supernatural. (Although, if I got to do it over again I would also have a more joyful ceremony instead of the traditional solemn one!) I didn't realize that had my foster father not been an actual minister I would have had to have had someone else sign my license. (If I got to do it all over again I would also choose a secular celebrant and have a pastorfarian ordained by the Church of the Flying Spaghetti Monster sign my license to make it official!)
Incidentally, if a couple believes that the person signing their license has the legal authority to do so, they cannot have their marriage license revoked even if it turns out the person didn't actually have legal authority. The person making the claim would be in trouble but it wouldn't affect the license they signed.
Marriage is, of course, a religious tradition that has been co-opted by governments to answer legal questions. Who gets what. Who's responsible for who. I share the opinion of many that government shouldn't be involved with marriage at all, that it should only be involved in civil unions, i.e., the paperwork, not the ceremony.
Getting married is simply what we're brought up to expect we're supposed to do. And...it's romantic. We could really do just as well having a "commitment" ceremony which is what many are opting to do nowadays, all the fun of a wedding without involving the government. Although, the government gives financial incentives for a couple to be married. I myself am technically married even though I've been "divorced" for years. It's just a financial decision, and a marriage license is just a piece of paper. But, I have two younger brothers with families and neither are officially married. Financially, that's the right decision for their situation.
Nowadays we can buck tradition and just do what makes the most sense for us. If you'd like to get an idea of what some other nonbelievers' ceremonies have been like, I can send you some "scripts".
I'm not sure what ever happened with your desire to challenge the law here in Oregon, but that exact thing is happening in Indiana right now. Hopefully the tidal wave of change across the nation will occur shortly after.
My wife and I were married ten years ago in a decidedly non-religious, though not explicitly atheist, ceremony officiated by Roger Moore, who works out of Portland. While he is a non-denominational minister, he was focused on making the ceremony precisely what we wanted, thus, no prayers, no biblical verses, nothing related to any religion. I don't know the capacity in which he signed our marriage license - I'd have to dig it up.
So, while not a specifically secular officiant himself, he worked with us to give us the ceremony we envisioned.
Hope this helps! Here's his website: http://moorecreativeweddings.com/