I find your post interesting because I worked with an autistic girl for several years and she loved drawing, when she drew things it was like she was creating a universe for herself. She had an amazing sense for proportion and movement and just like your son I think she would have done great in a field like animation with some training and support. Her favorite thing to draw was animals and she would often start on something like a horse and then make lots of drawings of different poses which were really accurate with the real world and then go on to creating different environments and building up complete animal worlds.
When it comes to Maya it's a 3d application and intended for building models and animating them, you can't actually draw in the program itself unless you use something called paint effects. Drawings can be imported into Maya to be used as reference images for building models, you also have matte paintings which are used in digital compositing for background landscapes and made in different paint programs. In Maya you have the main fields of modeling, making materials for models and lighting up scenes, dynamics where you create things like fire, smoke and fluid simulations and rigging/animation where you put in skeletons and make things move. Most people specialize in one of these fields and they're all very complicated and it will take a long time to get really good at. 3ds Max is similar to Maya and you can do the same things, they simply have different interfaces and different tools so when you know one 3d application switching over to another one is not too difficult as the principle remains the same. There are also lots of other 3d apps, Maya and 3ds Max are probably the most popular though and used by a lot of professional studios in the industry as they are fairly stable in all fields. So it's just a question of choosing which one to go with, because Maya and 3ds are huge it's easy to find a lot of training for them online but they are also some of the more expensive programs on the market. You can download free trial versions on Autodesk's site, as well the student and learning editions are a lot cheaper than the commercial ones. Mudbox and zbrush are sculpting apps, and they're commonly used to add detail on models, so you build a base shape in a program like Maya and export it to zbrush for detail sculpting (again they're as complicated and do more than this of course).
The problem with something like Maya is that getting started in the program is by far the most difficult part, just getting around the interface can be very frustrating and you do get stuck on a lot of things in the beginning. I can't remember how many times I almost tossed my computer out of the window (and still do for that matter
). Most people start by building models and then move on from there, but I also think a lot of people give up because they're expecting quick results and to create amazing looking things straight off the bat which is simply not possible for anyone. Once you get over the initial bump which does take a few months at least for most of us, things start to shape up a lot quicker and you can progress really fast.
For your son if he enjoys drawing I'd recommend you to get a 2d application to start with, Photoshop is really good and the program itself is just so much easier to work than any 3d application because the interface is much simpler and fewer things to take into consideration. In Photoshop you can draw and make nice looking ink sketches, play with photography and compositing and get something that looks good fast and I think it would be a great starting point in cg. As well there's tons of free tutorial sites dedicated to photoshop so finding good free training is really easy, and when you work in Maya you use it for a lot of things so you would need to learn a program like this sooner or later. Again you have other programs like Illustrator which is specifically intended for drawing and it's half the price, I've never used it myself so I don't know too much about it, but in video tutorials on-line for 3d apps Photoshop is normally the program they use as well so for this reason I'd go with Photoshop.
If you want to have a look at these programs in action we have some tutorials in the free section http://simply3dworld.com/movie_pages...html?cat_id=23
which will give you a better idea of what I mean. One is called "Character design" and it goes through the whole process of drawing a concept sketch and inking and coloring it in photoshop with a tablet. The other ones are "The cartoon dog" which shows how to build a simple organic model, "The bouncing ball" which goes over some basic animation, you also have "Dynamic object placement" and "Interior design" which are quite funny if you're new to Maya. So if you get a trial version now or later that's a good place to start. On this site almost all the training is project based, and focused around getting results and learning the program that way.
Another thing to keep in mind when you build 3d models is that organic models are more difficult for most people as you have to use your eyes and sculpt out shape, whereas if you start off building something like a house you can work off exact references which will make it easier and faster to get a nice result and it's a bit more rewarding. To integrate between two programs your son could draw up a nice house in Photoshop, bring his drawings into Maya and build it there. I'm going through all the content on this site at the moment and two tutorials that I found really good for someone who's completely new is "The Victorian House" and "The Haunted House", they're funny to follow along with without giving you too many problems along the way. Doing a few projects and building a some things would give him a good idea of how geometry is constructed and from there he could move on to animating things if that's what he finds most interesting.
I wish you the very best of luck and let us know how you do along the way. We have a work in progress section in the forum where your son can post up things he'd create for some feedback and there's a lot of friendly people here to offer help if you'd get stuck on something,