Underground 4 Day Ticket?
 

I will be in London 5 days and will be using the tube as my main mode of transport. Should I buy a weekly pass, single rides or daily passes? What are the passes called?

If you will be riding the bus/tube 3 or more times per day, then the 7-day travelcard is best. For fewer rides, then buy a book of 10 carnet tickets for the tube, which are good throughout Zone 1.

Here's the tube's own overview; you'll find 7-day cards under "seasons".

http://www.transportforlondon.gov.uk...t_tcards.shtml

do we need to furnish a picture for the 4 day travelcard?

No you don't ned a picture, but I believe the 4-day pass is available only on line in advance
the 7-day can be purchased there

Adults don't need a photo but children do.