Being a strong believer in the will of the Force, I'm sure he thought it was much more than a coincidence to be reunited with Anakin's former droids, who are carrying a message from Anakin's daughter and pratically arrived on his doorstep with their new master - Anakin's son! If that's not a sign of divine intervention, then what is?
Furthermore, I wonder if Obi-Wan was out looking for Luke (when he saved him from the Tuskens) because he either a) sensed Luke was in danger, or b) felt the presence of Anakin currently in orbit around Tatooine in his Star Destroyer and wanted to make sure Luke was not involved.
After seeing ROTS - I also wonder if, after Luke's decision to come with him to Alderraan and the obvious need for safe transport from a trusted friend, I wonder if Obi-Wan contacted Yoda, who contacted his wookie pal Chewbacca and set up a meeting at the Mos Eisley cantina. Or was that a coincidence too?