Eggs produced for hatching require a higher level of nutrition in the laying hen than those produced for eating. So to feed simply layers ration is likely to cause low hatchability, or chicks with signs of deficiency like splay legs. To add wheat will make it worse as you are then diluting the vitamins that have been added to the layers feed.
However, free range hens will normally source everything extra they need for themselves, so a standard ration will suffice. BUT they need to be properly free range with plenty of room to roam and scratch, not just with access to a small, initially grassed run that has degenerated to a smelly muddy bare patch.
If unsure, it is always better to feed breeder pellets. If poultry breeder isn't available then pheasant or turkey will do.