I wish there was a compromise, I am happy for the B&G and there families to receive the images, in full resolution as thats whats what I agreed, I just cant think of a way to ensure the guests and friends don't get hold of the images for free aswell
What are they planning to do with the images.? Probably going to get some printed somewhere. Just tell them you dont mind getting them printed for them at cost price so there is no chance of copies (except for scanning later)
I think you can sort this out ammicably without upsetting anyone just by being honest and not making any money for the B&G prints. I'm sure some guests will be slightly upset that they cant get them for free but remember that you are not a charity.
Offer them the full res pics on cd once you have made enough to cover your costs and a bit more.

