Let me use another example to illustrate my point. If a priest does not use the specific words "Take this all of you and eat it; this is my body which will be given up for you" - if he does not use THOSE words, then transubstantiation does not occur. If a priest spent his entire career saying mass and using a different phrase - no matter how the rest of the liturgy and ceremony and sacramental trappings may indicate that transubstantiation had occurred - I've got news for you - in not one instance did transubstantiation actually take place.
In the same way - regardless of children, longevity, public appearances, quality of life or relationship - if the basic requirements of making a free choice to marry with the intent of having children is not met - then an actual marriage never took place.
I would hazard to say you're falling into the same trap that all of the same sex marriage advocates are setting - if it looks like a marriage, and sounds like a marriage, and feels like a marriage - WELL THEN, IT MUST BE A MARRIAGE.
The end of such a marriage requires a divorce not an annulment. Be honest.
You can't have a marriage annuled without breaking the civil union, as well. As I mentioned above, if the marriage isn't valid when the vows are exchanged, it doesn't suddenly become valid later on.