Definitely plan some rainy day activities.
I've seen little ones spending ages just kicking up dry autumn leaves, so don't think you have to continually make suggestions of provide activities. Let them find their own amusement.
You seem to suggest they are coming from outside the UK. So find some typical things for them to tell their friends back home about. (Easy if you're in London, of course.)
Is there a steam railway near you?
A game of conkers is very British.
Ask them what they would like to do. Look at things from their perspective. Kids find walking in the countryside boring, and if you want to take them out for a walk, make it interesting before you start. It's no use trying to get them interested in collecting mushrooms/chestnuts/berries/pretty coloured !leaves if they are already fed up.
Museums in the UK usually have great programmes for kids - the 12 year old should be ab!e to find something they can do.
AI is here - Barclays is cutting 5,000 jobs
What job would you do now, if you had the choice? (Light hearted)
Aricle on what it's like to work as professional psychic witch



