random thoughts:
1 year - so about 8 months, 5 days a week, 1 hour a day. about 160 man hours. not a lot of time to work with.
you teach art, yet the class may cover much more than art. would you prefer it if the focus were more art oriented?
with individual study, you will learn the lingo and tools of making games (game development). always try to be precise with terminology when posting here. its very common for folks to require a few post until they're on the same page due to terminology (game design vs development for example).
first, i'd say its sounds like you want to teach "intro to game development", not "game design".
an overview of the development process might help here (i'll keep it simple):
1. you decide what to make.
2. you design the game. the rules of the game. how it should work. this is pen and paper work. or text editor. some folks say spreadsheets , but i personally haven't ever had the need. this is game design. nothing to do with art or computers at all. buy a copy of dungeons and dragons, classic edition. 3 pamphlets, about 40 pages each, teach you everything you'll ever need to know about good game design. balance, scaling, pacing, all of it. Dave Arneson (of Gygax and Arneson) was a rather gifted designer.
3. you choose tools to use to make the game. get or make an engine. get 3d modeling software (assuming a 3d game). get a paint program. get audio editing software. get them all to work with each other (compatible file formats for import/export).
4. you create meshes, textures, skinned meshes, skeletons, animations, level maps, music and sound effects, and probably a couple more things i forgot.
5. you import all these assets into the engine, then write scripts or code to bring them to life.
you say you want to keep it light on the coding.
perhaps the best option would be to have a simple 3d game already made, and have the class make all the graphics assets. use 3ds max education version, etc. the game would already exist when the class started, but with placeholder graphics. and by the end it would showcase the students artwork. this would be more of a "game art" class, than "game development" class. but it would also be a more real world art focused experience for the students.
real world games artist will get stuff like "make me a this, and it has to look as good as that, and you can only use 4 256x256 textures and 100 vertices total, and i need it in two hours - and no splines or convex hulls or tessellation. - oh, and rig it too, and here's the list of 37 animations we'll need. You're right! that's a lot of work! tell you what - have it ready by lunch tomorrow, the new level maps won't be ready until then. you can stay late if need be." IE the ability to create great art on demand with inadequate resources and time. teaching art students how to accomplish this would be the best possible for-the-real-world training you could ever give them.
if you're not trying to emphasize art, then there's nothing wrong with teaching "intro to game development". but the course length (IE lack of time) will limit what you can cover in a school year. i would say that teaching a 2d paint program and some 2d game engine that doesn't use scripting would be doable. 3d may not be.
you're really going to have to try it yourself first to see how fast you think you could teach this stuff to your kids.
i'd start with blender, or an academic version of 3dsmax or maya etc.
see how long it takes you to create, texture, rig, and animate a character model. that will give you a good idea of what you're up against.
if 3d starts looking like too much work, you can always go with the "game art"class idea, and just teach 3d game graphics asset creation in-depth.
or you can drop back to 2d with stuff like photoshop or gimp and game maker etc. but then you lose the coolness factor of 3d. and we all know how rare it is for anything taught in school to be "cool".
another possibility is to coordinate with the CS instructor for a join project between both classes. the CS students make the engine, and the art students create the graphics. both classes get coolness factor.
the sad fact is that with the limited length of time available, you just won't be able to teach them enough to make much of a 3D game. one character that runs around an empty Unity level using scripts you provide would probably be about it. but they would learn a lot about 3d game art.
the best thing to do is try it yourself first, and see what times are involved.
for tools, look to 3dsmax education version. maya and other may also have academic pricing programs. blender and gimp are free. photoshop is the industry standard for 2d work. they too may have an academic version.
read up a little on game design, grab some tools and start checking them out. once you get an idea of whats involved, you'll be in a much better place to judge what is "right sized" and the "right direction" for the course curriculum.
honestly, just creating a character mesh, texturing it, rigging, it, and animating it is probably enough to fill the entire school year. especially if you teach a few advanced techniques such as creating matching wardrobe, multi-part meshes with interchangeable heads/limbs, and so on. and you can always have a stupid little unity demo for the students to try their characters in. that would make the class both art focused and real-world relevant - and 3D!. gotta get that coolness factor in there! <g>. nothing makes learning easier and more fun than getting to learn cool new stuff.