We have 2 adults and 3 children traveling in May. We have 4 days, not in a row, in London and I've read it's cheaper to get a 7 day travel card and put it on a oyster card. I've looked at buying these ahead of time at Visitbritain.com, but I can't see the children's price on the oyster card, only a certain amount of pounds I can load on the card. How can it tell it's a child card? VisitBritain hasn't answered my question yet. On the 7 day travel card it only shows a pass for 7 days, all 6 zones and we only need zone 1 & 2. Has anyone purchased these ahead of time or is it easy to purchase in the station there? Anyone have experience in this?
Oyster has a lot of info on the website www.tfl.gov.uk. I would recommend that you just wait and buy your Oyster Cards after you arrive. I loaded a 7-day travel card on my Oyster Card two years ago. It worked very smoothly. On exiting at Tube stations a small screen will show the amount of money remaining on your card. During your 7 days, that won't matter. I even used my 7-day card in the Heathrow area on a bus and it was accepted.