I'm not one for astrology or other superstitions, but i have to say i do like a good portent in the sky. I got an iPad recently, and one of my favorite apps for it is the amazingly sweet "Star Walk" (iTunes link) astronomy program. When i found that you could zoom around in time as well as in space, i immediately fast forwarded to our wedding night to see what the sky would look like. As it turns out, it will be a new moon and three planets will be really closely aligned at sunset:
The other thing that was really cool though is to the north. I didn't realize it when we set the date, but as it turns out there may be some Perseid meteors visible that night, and i bet we would have a fairly amazing view of them from the mountain. They might not be really visible until much later, but man what a sight that would be to have the meteor shower flying over a volcano at you? Hell yeah.