Traveller's Cheques are heading the way of the dodo, and often incur curious stares or additional fees (except at the AMEX office, of course). Purchase them in Euros if you must use them. Better yet, avoid them.

Otherwise, get him an authorized user card of your Patinum card AMEX card (no forex fees) for higher price credit card expenses such as lodging or medical care (but be aware many locations will not accept AMEX cards or may charge additional fees), and an ATM - check for corresponding banks that may not charge a foreign bank transaction fee. (see andreadbc and Palal.) Also see qvzn's recommendation of the Schwab card.

Unfortunately, most American cards do not have an EMV cjip (allowing chip and PIN use) - a few do, but mostly they are the "chip and signature" cards. Some merchants, especially smaller ones and those with untrained cashiers - sometimes do not know how to handle the magnetic strip card most commonly used in the USA, as their terminals read the EMV chip and ask for a PIN number - though most have the strip reading slot, some may not know how to make use of it.

(The only chip and PIN card is, AFAIK, the US Diners Card - which is actually a Diners branded MasterCard, with chip and PIN EMV - but they charge 3% forex fees.)