South Pacific islands are expensive. Twice what it would cost in the US. Until you reach NZ. but as mentioned, ATMs are everywhere, so if you have a debit card or credit card, you're set. even where there is no atm there will be a bank, and your credit card (VISA or MasterCard) plus your passport will get you a Cash Advance in a bank. So don't carry more cash than you can afford to lose.
Advantage of an ATM is that you will be getting the money in the local currency. A few exceptions - If you go the the Gambier or austral Islands of French Polynesia, I'm not sure that you can get cash - so you'd need some for there. Otherwise, pretty easy.
Time. You will arrive in NZ around November, first week of December. - start of cyclone season, so you don't dally later than that. when you leave Panama? Usually April, perhaps as early as March.
Sorry if this is choppy, I'm bsck to using cybercafes. Kirk, will email you in next couple days.