Plaça de Sant Jaume is not necessarily a highly known tourist attraction due to the fact that the Government’s building is located here, hence this site has important political means. The building can be entered only one day a week, and therefore, not recommended for families with children (for additional information- Attractions and Tours in Plaça de Sant Jaume and Attractions and Tours in Barcelona).
Even though the building itself is not family friendly the area in which it is located, the Gothic Quarter, is highly enjoyed by children of all ages. You can take a tour in the quarter and stop in the square to explain your kids about the history of Catalonia the culture and the political situation (for additional information – History of Barcelona). Not every family is interested and willing to explain this to their children but if you would like to – this is a great place to do so.