When the pipes are repaired, make sure they check for voids under the slab. If there are any, they should be at least concreted to eliminate them. A more professional but also more expensive way is to mudjack them - pump in grout under low pressure to fill all voids.
Unless these cracks are vertically offset or more than about 1/8" wide, I would wash out (or use compressed air) and a sharp pointed pic to clean the cracks after the pipe is fixed, then fill the joints with a creamy mix of portland cement or concrete fixit type grout (preferred), or you can get concrete caulk that comes in tubes for a caulk gun and caulk the cracks, smoothing it with a wet putty knife. Then watch their growth over time - if just a gradual hairline crack that does not vertically offset across the crack or grow more than an eighth inch wider over a decade or so, then I would not worry and would just close it back up with grout or caulk periodically. Obviously, while this is growing, putting any type of tile or stone floor on top of it would not be a good idea, as the crack will propogate through them too. A floating floor should be no problem, but of course you loe the ability to see how much the crack is growing.
If you can describe how the cracks run relative to walls, doors, etc it might help to understnd what type of cracks they are, especially since you said they have been there since the house was built. Also, are there matching cracks in the foundation walls ?