This will determine whether I need to pick up 7-day
Travel Cards or just work with day offpeaks.

Just to make sure, did you notice there's a special Visitor Travelcard?
http://www.tfl.gov.uk/tfl/promo-visitor-overseas.shtml

I had one for Zone 1&2 each time I traveled to London, making things a
lot easier for me, as I never needed to care about daytime or whatever
but just could use the underground or a bus when I liked to.
Even if - or especially when - you're walking a lot, you'll be glad not
having to walk all the way.


Regards,
Joachim