Well this is really new, I have not thought about this but if the person wants to why not right? There are no rules that you can't make bitcoin as a wedding gift. Especially if you know that the couple knows and have the knowledge of bitcoin why not right?. In that way they have money online that they can invest on in the future especially when they will have kids. Its important for them that they have savings and I know by the time in how many years bitcoin will be known all over the world and surely the market price of it is over board than what we have right now. I never thought of giving bitcoin as a wedding gift but its really up to you. As I said there is no rules of it that you can't and the couple won't deny it because its a gift. You gave it for a reason even if they don't know about bitcoin you can teach them about it so they have an investment for the future of them.