Using a D800 to take pictures of pictures...

I've been visiting my parents for the last few days and just discovered a ton of great, and old pictures that I fear are aging and could be damaged. I only have a day left here and I'd like to try to take pictures of their pictures with my D800, but I'm not entirely sure how. I don't have a macro lens, which would probably be best. Here's the gear I do have on me:

Lenses: Nikon 28mm 1.8G, 50mm 1.4G, 85mm 1.8G
SB600 flash with umbrella and stand (no boom arm though), radio remote flash trigger

I'm not sure how I can use the light in the most neutral way to capture these images. I'm open to ideas! Any thoughts appreciated. Thanks!!