In order to use the "Kid for a Quid" promotion for tube travel for 11-15 year olds, it says the adult must have a travel card. Does it actually have to be a travel card or can it be an Oyster card?
Here's a quote from the Transport for London site: "Up to four 11-15 year olds accompanying an adult Travelcard holder can buy a Zones 1-9 Off-Peak Day Travelcard for just £1 each. Just make sure that the adult holds either a valid printed Travelcard
or an Oyster card holding a Travelcard. Off-Peak includes Monday-Friday from 0930 and all day at weekends and public holidays."
The way I read that statement, you can use an Oyster card if you load a 7-day travelcard on it but not if you use it strictly as a pay-as-you-go card.