We decided to walk around the outside (sea side) of Valletta to see what we would find. The answer was a reasonably constant stream of good viewing angles plus a theatre which shows a short documentary about Malta's long history.
The full circuit brought us back to the main gate of Valletta in time for lunch in the shade (now 26 degrees).
The cannon that they fire at 12pm and 4pm. They also seem to fire several of them (if paid?) by departing cruise ships.
After lunch, and the wedding, we decided we really needed to get out on the water for this perspective of the city too.