Digital BW, The Print

Maybe someone can help me here... 

I printed a large project a year ago on FB paper, on 11x14 paper, and 
these final "master" prints were intended to be used for a high-
quality book project. These prints are the only ones available - I 
couldn't afford to print several copies. 

These prints are going to be sold at an exhibit soon, but I would like 
to keep an exact "digital copy" of the image as it is on the print, so 
that there is consistency in the look of the silver print and the 
image on the (upcoming) book. On the other hand, I might want to make 
digital negatives of these images later on to propose more affordable 
versions of the image. What would be better, keeping in mind that 
image quality is the first priority: having the prints drum-scanned 
and "ready" for any sort of output (book, digital negative, inkjet) or 
drum-scanning the 4x5 negatives and re-doing the work on the computer? 
Also, what's the least expensive of the two, considering that I would 
be doing this to 50-70 images through a service bureau? 

Any help would be great. 

Thanks, 
SR