Rather than the other options which are:
A day out at Chessington
A day out at the Enchanted forest
A river cruise from Greenwich to London and back and then some time at the Naval College
A day out to the Hop Farm to go tree treking?
They are pretty knackered at the moment and DD has some entrance exams coming up and I think they would benefit from the rest. We've also got a busy weekend coming up. But it is supposed to be a sunny day tomorrow.
My suggestion would be a quick trip to Blockbuster now to stock up on a few DVDs and a packet of popcorn. Then a day spent snuggled up on the sofa watching films!