Kids Week?
The view of London's skyline from the 7th floor of Tate Modern is truly interesting - as is the view from one of our regular pull-in places Greenwich Park. A boat to the Thames Barrier is exciting Andy (us old gits on bikes use the Woolwich ferry as a substitute!), There are usually mime / buskers on the South bank adjacent to the Wheel...there is a DUKW - amphibious boat that trails around London then dips in the water - looks good fun but maybe expensive - don't know.
I always like Trafalgar Square - maybe take your children to Admiralty Arch to play 'find the nose', either walk to Parliament from there, and thence The Thames, or go the other way and nip into the national gallery and one of my favourites, The National Portrait Gallery. Vernon's idea of the welcome is good - I was surprised to see it.
There is what looks like a super children's playground - the adventure sort ,in Parliament Hill Fields (another ride route!) Great views 'downtown' too, café and a C2 bus gets you there, from Victoria, via Regent St etc.
Changing of the Guard is on odd days in August. Erm, what else...Go and see Bent Mikey teaching people how to skate in the shadow of The Albert Memorial!, Get ot Wellington Arch in the middle of Hyde Park Corner and see the sight of the departs for the FNRttC and the London Sunday Ride
I think you can go upstairs in the Arch as well. Fabulous Australian soldier's memorial there, and there are often historically dressed soldiers with muskets, pretty drums etc. tooling around doing drill and posing for photos...all very civilised.