First of all, it would be very important to have the correct due date. Most dog owners count 63 days from the day of breeding, when to be accurate, one must count from the ovulation date in order to time when a C-section should be done. In general, if done too early (like 4-5 days earlier or more), there are risks that the pups will be premature and have insufficient lung development to survive.
For this reason, it's important to have progesterone levels monitored prior to doing a C-section. Based on the results, the vet can determine whether it is safe or not to do a c-section. Generally, it is safe to do a when progesterone levels drop below 3 ng/dl.
Other parameters to consider is whether the dog is starting to produce milk and showing signs of imminent whelping (nesting, temperature drop) and how the pups look on ultrasound.
So deciding whether it's too early to do a c-section takes more than just marking a date on a calendar. It would be important making sure all the parameters are met and when your veterinarian feels it's best. It's unfortunate, but sometimes c-sections are done too early in fear of weekends/holidays and vet's offices being closed and things don't go as well as planned.