It depends on how much you will ride versus walk, and how many extra trips you will make.
There isn't a 6 day. It would be a week
Everything you list, including Euston and Notting Hill Gate are in Zones 1 and 2. Travel beyond Euston will presumably be paid by your tour.
If you plan on using the 2 for 1 plan offered by the railways for some of your attractions then a railway issued paper Weekly Zone 1 and Zone 2 - cost £35.10 per person plus a passport sized photo is a good idea.
If you don't plan on using the 2 for 1 savings then an Underground issued 7 Day Zone 1 and Zone 2 Travelcard added to your Oyster Card with some extra funds for any trips beyond Zones 1 and 2 - if you decided to go to Kew Gardens, say, or to or from an airport, - same price for the Travelcard, add for the additional Pay As You Go money - might be a good idea.
If you mostly intend to walk, or at least ride less than the daily caps, then just a PAYG Oyster with some funds on it, top up when it runs down, might be a good answer.
Even with you listing all your proposed destinations I expect that you will want to visit other ones and make trips to restaurants and other trips, and so much depends on your style of travel and desire for the 2 for 1 tickets.
Bet you wanted a clear cut answer, eh? Sorry.