When are you getting married? If it's going to be in the middle of summer, make sure the butterflies are kept somewhere cool- I've read of a couple who opened the box, flung their arms up as instructed and had dead butterflies rain down on them. Not romantic at all.

That said, I like the idea of waiting till everyone's out of the chapel, and gathered round you in a big circle and watching as you release them. Maybe have somebody at the end of the ceremony instruct the guests in what's going to happen?

All the best and congratulations on your upcoming marriage!