Help me plan my weekend in London

[Longchip]

I’m taking 5yo to London next weekend and need some advice on a fun & doable itinerary. So far I’ve got:
Arrive in Euston Friday evening (picnic tea on train), then head straight to the hotel -CitizenM next Tower of London.
Saturday we’ll be seeing My Neighbour Totoro, 2-4:40 at the Barbican.
Train back Sunday 6pm.

We like to do the Tower of London tour, but wondering whether to do this first thing Sat, or Sun. What else is fun for a 5yo? She has already seen Andy’s (aka Natural History) museum and Buckingham Palace, but was too tired for Big Ben last time so we’d like to swing by there if possible. I’ve enjoyed the Tate modern but is it any good for a kid? Any tips on what to do, how to get about etc?

Skygarden is good to orient yourself - make sure you book

My DC liked the quieter galleries and Tate Modern at that age, more so than busy museums - and nice to wander along South Bank if weather decent

Tower of London a must with the ravens etc

Buses are fun and see so much more than in the tube but very best way is just to walk

Walk across Westminster Bridge for best view of Houses of Parliament

Take an Uber boat down to Greenwich