I heard Damu Anna was childless. How does the Satcharitra describe Sai Baba's intervention in this matter?

Yes, the Shri Sai Satcharitra confirms this. In Chapter 25, it is explicitly stated that 'Damu Anna had two wives, but he had no children.' The text directly attributes the resolution of this issue to divine grace, stating, 'By receiving Sai's blessings, he was blessed with sons.' This detail is presented as a powerful example of how Sai Baba fulfills the desires of His devotees and removes their suffering. It is mentioned in the context of Damu Anna's deep and consistent devotion, exemplified by his vow regarding the festival flag, reinforcing the theme that faith is rewarded.