It is best to contact your doctor about post operative care and instructions since each doctor has a different regimen.
Whey protein shakes are not a problem what so ever even pre-op. What can become problematic is blood thinning from certain supplements. Always check with your physician before taking supplements.
Protein and vitamins can be in use after a week of your operation. İf you are asking for body building purposes you can use it however do not use steroids.
You could have a protein shake the next morning after a hair transplant if you wanted. So at a week you are even better.
It is ok to take Whey Protein Shakes after a hair transplant providing that they do not have anabolic steroids in them,