Yes, children can pay for travel with contactless, but it cannot be capped at this time.
Even if your child doesn’t have their own contactless bank card or device, there are a number of prepaid contactless cards children and young people can use to pay, such as The Rooster Card. Other products are also available.
Just request the child ticket(s) required from the driver and indicate that payment will be made via contactless. As the machines are set to single adult travel by default, you must wait until the driver prompts you to tap your card otherwise an adult fare will be applied. If the transaction is approved, the child ticket(s) will be printed along with a receipt.