Animal Kingdom is a great place to take your son if he isn't afraid of animals. They have a wide variety of shows and rides for younger guests. Dinoland USA has a load of stuff for him to do including Dinorama (carnival games and rides) and The Bone Dig (giant playground). One of my favorite attractions there is the Kilimanjaro Safaris ride in Africa where you get to see tons of live African animals in a natural setting (bring your camera!). There are tons of things to look at throughout the park, tons of shows (Flights of Wonder and Finding Nemo:The Musical being my favorites), and various trails you can take to see animals. Animal Kingdom is the largest park on property, so be ready for a load of walking!
Magic Kingdom is probably best for a child his age, as they have the most family rides. Fantasyland has a lot of rides for younger children, but there are lots of attractions in other areas of the park as well! Too many things to list there :P
MGM Studios seems to not have too many things for younger children, but various areas have some stuff he may like. 2 of the biggest attractions there are thrill rides (not for 5 year-olds of course :P) but there are several other good shows and various things to do there.
Epcot probably isn't the best place either, but some of the stuff there can be enjoyed at all ages. Innoventions is a great place to take him where they have lots of games using the latest technology (so many things to do that it fills up two buildings, Innovations East and West!). A semi-hidden jewel would be Station Cool (by the Fountain View Bakery), where you can sample various sodas from around the world. One of the better things for young children is the recently-remade "Seas with Nemo and Friends". It used to be called the living seas but is now themed around the movie Finding Nemo, and you can go through (on a ride as well) and see various fish and other marine animals. The other side of the park is The World Showcase, featuring 11 pavilions, all themed around different countries. In each country, there is a kidkot station where you can get a mask and visit each station to get various decorations to put onto it (its a great thing to make him look foward to each new pavillion).
There are TONS of things that I havn't mentioned, but I listed some of the things I think he'd like to do :)
There is a Downtown Disney area, which has 3 sections: Downtown Disney West (various non-disney stores), Marketplace (all the disney merchandice you'd ever want), and Pleasure Island (night clubs and hangouts for adults). Downtown Disney West has a Magic Masters store, which is a must-see in my opinion. Whenever people come in they perform various tricks that they sell at the store and its very entertaining. Marketplace has tons of stores, all selling Disney-related merchandice. There are so many stores to visit, with all different themes (its hard to say which ones are best!).
I'm not positive about the shipping things to you home, but I know if you are staying at a Disney resort you can have things you buy taken to your resort for you. I'd call and ask about shipping things to home, I doubt there isn't something like that!
Good luck to you and your son and make sure to have fun :)
Message me if you need more info about various things!