I'm glad you have a foot care routine! Be careful with the ped egg as those types of files can take off more than is ideal causing the callus to grow back faster and thicker over time.
You mean if the cracks are open and bloody? I'd start by recommending the client use Gehwol's Salve for Cracked Skin to keep the cracks clean and start to return elasticity to the skin. I'd avoid this area in service if they came in this way.