Bank / Travel card for teenagers recommendations

[Poppiesway1]

Hello..
ds is going to the states in the summer to stay with family for a month post gcse exams. Has any one got a recommendation for a travel card he can use for spending money? (Which I can top up as when needed while hes away). This is the first time he’s been away without us there to pay for everything (he doesn’t want to keep asking his aunt/uncle to pay and I don’t want to send him loaded up with actual dollars)
I currently have a Post Office card which has been good, I’ve emailed to ask if I can have two linked to my account but no response as yet.
has anyone any experience of their dc and spending money abroad (he is 16)
thankyou!

[BlueChampagne]

Something like Revolut or Nimbl?