I would both scan them for possible inkjet replacement (check the decals forum below for more on inkjet decals), as Gene suggests, and stand by with Decal Film. One could coat the sheet with the decal film on speculation of problems, or test a decal. Most decal sheets have some artwork that is not needed for the model, such as the brand logo, and sheet identification number. These areas are actual decals (don't know why they are- maybe whoever prints/silkscreens doesn't bother to rationalize, just makes all non-clear areas decal). Try one of those areas to see if decals shatter.
If so, then apply decal film to rest of sheet. Micro Scale is the most popular brand of Decal Film, but there are several other brands too. This stuff is made just for that problem.