You've probably already decided what you're going to do.
I personally would want to hand-deliver it if at all possible, so as not to risk loss in transit. Most couples don't open their gifts right away unless they're postponing a honeymoon, so there's not much chance of you seeing them open it in front of you. But if there IS a chance of seeing that, I'd definitely want to see their reaction. But I'm no good at rushing--I tend to make mistakes and regret it. On the other hand, I work better with deadlines. I"m no help, am I?