I was only in London for about 3 years, I loved getting bagels on a Sunday morning along with a newspaper that took a week to read.
@mogloveseggs I took my cousin to London when I was living there, he was about 10 or 11 and only wanted to go on the tube and tot he top of a tall building, I had a friend who worked in Centre point tower so that was his tall building, on and then paddling in the Trafalgar square fountains.
How old is your son?
One thing I've done on a couple of city trips is to get the hop on hop off bus and take a map / notebook, when the bus stops or goes past somewhere interesting that you want to explore then mark it on your map and make notes.
If you are going to take him then it can be cheaper to book a short break including a theatre show than just booking a hotel (when theatres are back that is).
So book a 2 night stay with the show on the first night, spend the day on the Ho-Ho bus deciding what to see the following day and seeing some sights. Plan for when there is 'something' on so if you want to go to Buckingham palace find out when the changing of the guard is and see it then. Pick up a copy of 'time out'.
Go to the hotel to freshen up go see the show and have evening meal, back for bed .
Day 2 go see all the places you noted but didn't see yesterday. Spend the evening doing something from time out, obviously this depends on the age and maturity of your ds, I used to go to a pub that had free comedy open mike nights, I've also been to a couple of concerts at Kenwood house, they are on in the summer and you can pay and go in the posh seats or you can just sit on the grass with a picnic, the concert ends with a fireworks show.
Back to the hotel to sleep.
Last morning Camden and or Convent Garden for some shopping then home.