I dont have a problem with any of the recomendations but please check opening times before you travel.
It is Christmas and I guess many places will be shut. And we may have rail strikes!!
Enjoy your trip.
I was going to mention both these points, which tend to happen in the UK at this time of year. The tubes are working, so an Oystercard will get you here there and anywhere within a huge range of Central London, but outside zone 6 (Zones 1-6) you have to pay separately for transport. Depending on where you're staying in London might influence where you can get to outside the capital, as getting across the city can often take as long as getting to the outside the city destination due to various factors.
That said, all the suggestions are great, you'll be spoilt for choice!