Platform 9 3/4 and the Harry Potter shop at Kings Cross station.
The Lego store in Leicester Square is more than just a shop. It’s an experience in itself - it’s the biggest Lego shop in the world and has some massive models of London landmarks and movie characters. It’s also right next to M and M world which is great fun.
Inamo is a fun restaurant serving all sorts of Asian/oriental dishes. The food and the service is good, but the best bit is the interactive tables! Each table-top is interactive, on which you can order your food, graffiti, play retro games like battleships with the rest of the people on your table and customise the mood/lighting. You can even watch your food being prepared on a 'chef-cam'. There's a children's menu with some simple dishes like BBQ vegetable noodles, spring roll and Korean chicken wings.
Alternatively, go to My Old Dutch for the best selection of sweet and savoury pancakes. My DC like the chilli con carne or Italian pancakes, I like the asparagus one and DH likes the chicken curry or Dutch Hot! They also serve salads or you can build your own pancakes. Make sure you save room for a sweet pancake though. Last time we went, we had the Star Trek on Nutella pancake which was massive and had maltesers, Milky Way stars, Ferraro Rocher and ice cream!
Gordon Ramsay's Heddon Street restaurant has an ice cream bar. Children up to 12 eat free from the children's menu AND get an entertainment pack. The same applies at the Bread Street branch but I'm not sure if they have an ice cream bar.
The Transport Museum is great for children that age and there’s a new gallery called Future Engineers www.ltmuseum.co.uk/whats-on/year-of-engineering/future-engineers