I think 11 is a bit young to be trusted with unlimited cash. Let grandma have control

I’d say grandma is in charge here. Give her a card or some cash. Or sort it out afterwards.

How wonderful for your daughter. I’ve found the Qantas travel card to be good. The exchange rate isn’t fantastic but the service has been good, especially if something went wrong when OS

I’d be giving her Cash and putting Grandma in charge of safe keeping the bulk of it. Topping up the child’s purse each day. Spending up to the child.

Both bankcard and cash.
How much expoerience has the child has with bank cards ? Given the age of the child I would probably give her a limited amount of money – cash – to spend and have the grandmother overseeing the rest / bank card and hand out more when needed.

We have always gone with a combination of card and cash with sensible amounts for spending.

Just check with your bank, most these days have free fees over seas. iNG does

Your bank might have the option to have a foreign cash card preloaded with funds. I usually get the ones purchased at the post office. Having some cash exchanged already is a good idea, too. Keep an eye out for a good rate.
She is going to love Singapore. Such a wonderful place to visit.

i would personally give some extra money to grandma for her to buy as this is too young to spend in overseas county. and Singapore is pretty expensive than Australia. So it is best to avoid giving big amount

I agree with finding an age appropriate means of spending money overseas and that also avoids fees. A bank can provide good advice.

I would get a few dollars changed over in the currency that Singapore uses and then asked the Grandmother to manage the remaining money. Your child is probably a bit too young to have too much money while travelling overseas. I would be very conscious about giving a child too much money.

I’d speak to the bank and see what they recommend for that age. Alternatively maybe give the money to the grandmother to use for her as needed?