Disney Gift Cards will give you a better exchange rate than buying directly through the bank or charging to your credit card. I've been tracking the exchange rate that my Canadian Disney GC converts over to and it looks like they are just taking the end of day FX rate from the previous day and converting at that, which is better than anything you will get from a bank or currency store. The exchange rate will fluctuate, and if you have time before you travel you can watch the rate and buy some cash if you want to lock in a particular rate. When it comes to spur of the moment purchases, if you have the cash on a Disney GC, Disney will give you a better in the moment FX rate than your credit card will as it more than likely will charge you a 2.5% foreign transaction fee.