Hi, just to expand on the already mentioned ideas... my boys really love the launch pad at the science museum. On the top floor and is full of interactive things. Is free but can get crowded. Is one of their favorites... there is a new darwin center at the natural history museum which is great and all about how scientists study the natural world. He may be a bit young, but if he is into that sort of thing, might love it. You need to book tickets ahead of time, but they are free, and if you have a ticket, you can cut the long que waiting to get into the museum. while you are there, the dinosaurs are a favorite as is the creepy crawly room. It can get really crowded during prime times though... and even though hamley's will be crowded, kids love it, and it can buy you some shopping time on oxford and regent street! Also, some of the other museums have kids activities. Check the local time out for info, but the victoria and albert usually has a kids cart with activities for kids, and the tate modern has a great kids pack which takes the kids into different rooms to explore some of the work. That is a great museum to visit, and not far from the london aquarium, which is not the best i have seen, but the kids love it. There are lots of shows for kids around christmas time, and you can check out lastminute.co.uk for some reduced price tickets, and there is also a theatre that has shows for kids in shepards bush that are good and not so expensive. and I would get an oyster card, which lets you go on any train/bus and just takes off the correct amount, and your son can go free with you. and just take a regular double decker bus, as he can get the experience without being stuck for hours on one of the tours buses... and there is a great playground in kensington gardens (diana playground) by hyde park that kids love for a break. just a few thoughts! we have spent alot of time around london with 2 boys, so if you need any help, let me know!