We're going to be in the Netherlands this coming spring, both before and after our 21 Day Best of Europe tour. Since we are museum junkies, it will no doubt be to our advantage to purchase museumkaarts. I do understand that they are only good for 31 days; that works (just barely.) Does anyone know if we can pay for them with a credit card? We will probably be buying them at one of the museums in Haarlem. If we must use cash, that's fine; I'd just like to know ahead of time.