I'd just hand over the negs, except for the ones you value as part of your portfolio. Controlling your negatives is for professional gigs where you make money off the reprints.
For the really nice ones, explain to your friends why you want them (ie, part of your portfolio, a valid concern) and give them good enough quality scans that they can go and make nice prints from the digital files. If they're going to the drugstore for prints they're not so discerning that they need the originals.
If they're stubborn about this, they're assholes. It's your work and you did them a really huge favour, saving them a ton of money. You might remind them of the cost of a professional wedding photographer.