If they have a bitcoin wallet, then why not give them some of your bitcoin? it is not bad to give some of it and I think newly weds will also appreciate your gift because you still give effort to give a gift to them and if they already know about bitcoin and they also have bitcoin, for sure they will really love your give and save it for their budget for their honeymoon. 
Why not? but true to your word Yes if if they had botcoin wallets well what if they don't have? Anyway if they know about the previous bitcoin and whether the use and how to use. and when they had a bitcoin wallet then I will still give some bitcoin kan was also useful for the future or to suffice a little of their needs. This is not a bad idea even is good, we can also introduce bitcoin on them later.