We'll be in London in mid-June with my niece and nephew and plan to take in the Harry Potter Studio tour. Planning on taking the tube/overgound to Watford Junction. After the tour, I was thinking we could travel over to the Westfield John Lewis store and show the kids the Olympic stadiums and village. Looks like we can take the overground from Watford Junction. Is this correct?
We (the adults) will have zone 1/2 7-day travel cards. How much extra should we put on our Oysters for the additional zones? The kids (8 and 9) travel free with us, correct?