Assuming that the bride and groom are okay with it ...

If you are shooting 4x5 hand-held (Speed Graphic et al) use it to shoot something different from the main shots taken by the contract photographer. Candids, unusual vistas, kids playing off to the side, parents finally relaxing and maybe a casual portrait or two of the bride and groom.

Then give them an album of contact prints.

That way you will truly add to the record.