Help London travel

[FesteringCarbuncle]

I've posted before about travel around London so apologies for that
We are going next weekend. I decided that contactless was our best way to travel
I have a debit and credit card. I tried the credit card just to check because I've never used it contactless and it didn't work. The company insist it was a blip but are sending another. It is not guaranteed to get here
I need it for DC who doesn't have their own card. If it doesn't come what can I do at short notice so DC can travel around London?

How old are your dc? Children travel for free on london transport.

If the DC are travelling with you, you go to the big gates and use your debit card to tap and you all go through together.

If they are travelling on their own, by a paper travel card or a visitor oyster

buy not by

They are 12

In that case, get a visitor oyster card set to the 11-16 discount which is free bus travel and half price on tubes.

All info on the tfl website