Since 2002, the Euro is the only currency accepted for payment at Disneyland Paris.
Though the spread of the Eurozone, payments by credit card and cash dispenser withdrawals have somewhat replaced the function of Currency Exchange desks in recent years, the resort still offers the service at all the following locations.
It's probably best to exchange currency in your home country. In the UK, you can exchange currency at Post Office branches commission-free. If you'd prefer not to travel with so much money, travellers' cheques can be cashed at Disneyland Paris but are not so widely welcomed elsewhere in France.