Thank you for the replies. I appreciate the tips.
We were planning on "tweaking" his plan to some degree. I know one day we will be swapping his Westminster afternoon for his Churchill and National Gallery afternoon because Westminster closes early on Saturdays. We were also planning on scrapping the Southbanks tour in favor of other areas of London that hold more interest for us.
I was primarily interested in the timing. He has lots of "street walks" built into his day along with some major sites. It seems to be a bit much for one day, was just curious how real experiences add up.
In addition, I thought having Churchill War Rooms and National Gallery in one afternoon wouldn't really be possible. First of all, it seems like a lot of "museum" back-to-back time. Secondly, I would suspect you could spend an entire afternoon in National Gallery, so I wasn't sure if including Churchill would be wise or very "doable". I suppose it comes back to your interests as I see us spending more time in Churchill than National Gallery.