Of course, there is a great Transportation Museum, a bit east of St. Paul's Church?
That's likely to be the
London Transport Museum just to the east of St Paul's
Cathedral. Don't upset the natives
Only you will know if a transport museum full of buses and bits of trains would be of interest to your family members, but if not they might find the cathedral worth a visit. It was built to replace the earlier 13th century one, which was gutted in the Great Fire of 1666. More than 270 years later it survived Hitler's bombers.
As an aside, last week I found a documentary, recorded a few years back, called Britain From the Air. We learned that from 1946 to 1948 the RAF carried out a comprehensive aerial survey, flying in a grid pattern, to record the damage in preparation for rebuilding. St Paul's was standing alone in a large area of blitzed buildings. There's an
archive screenshot here. The documentary went on to show parts of a recent similar survey.
There were reports in more recent years that Hitler had ordered that St Paul's and Parliament should not be bombed as he wanted to claim them for use in propaganda.
Probably a lot more info there than you really wanted