Fast answer
Use Locorotondo as the hinge, not as an excuse to overload the day. The clean version is a trulli and white-town loop built around Alberobello and Cisternino, with Martina Franca saved for the bigger old-town evening if the group still has energy. Monopoli belongs only as a coast-versus-inland pressure check, Trullo Marziolla gives rural context, and rail or partial-car plans need live transport checks before they become route advice.
If you only do one thing
Default to a car-led Valle d'Itria loop: choose either Alberobello plus Cisternino or Alberobello plus Martina Franca, then keep Monopoli as a separate coast decision unless the trip has enough time and energy. Check drive timing, parking, monument access, crowds, weather, and return logistics before locking the order.