Why did the doctor's family decide to go to Shirdi when the boy's uncle was a doctor himself?

The decision to travel to Shirdi was born out of complete desperation, as detailed in Chapter 34. The boy's uncle was indeed a degree-holding doctor, and he, along with other physicians and expert surgeons, had tried every possible treatment for the boy's bone-cyst. They exhausted all native and foreign remedies and even attempted surgery, but the disease showed no improvement and the young boy was in immense pain. Having reached the absolute limit of medical science and feeling helpless, the family heard about Sai Baba, a famous saint in Shirdi. Going to see him and trying his Udi was considered a final resort, a way to 'cross over' the calamity after all other options had failed.