What was the main concern of Tarkhad's son about traveling to Shirdi, and how was it resolved?

The primary concern of Tarkhad's son about traveling to Shirdi was the potential interruption of the daily worship at home. Chapter 9 explains that he was worried about who would regularly perform the worship and make the Naivedya offering to Sai's image. This was a significant issue for him because his father was a follower of the Prarthana Samaj, and the son felt it would be wrong to impose the task of idol worship upon him. The conflict was resolved when his father, Babasaheb, gave him a firm assurance, promising to personally continue the daily Naivedya offering and ensuring no one would eat before Sai was served. This promise convinced the son to make the journey.