Yes. It does ship to Australia unless otherwise noted, and they do accept credit cards.
If you buy from different sellers, they will sell you separate packages, and you will usually have to pay shipping for each individual item as well. If you look harder, you might be able to find some stuff from the same seller and you won't have to pay shipping for every single item. (But if you don't find a seller who has multiple items, you'll be fine; the shipping is usually pretty cheap if you order it with the inexpensive, semi-slow shipping.)
Amazon is good, I've used them many, many times (for Tamagotchis, Warriors books, an iPod nano, and all kinds of other stuff) and have never been scammed. It's perfectly safe; just ask your parents first because they'll need to create an Amazon account if they haven't already made one.
But be patient with shipping! Especially with Amazon US, it might take a while to get your items all the way to Australia.