They're not talking about a specific product when they refer to "creative cloud," but rather grouping a number of graphical authoring products under a single umbrella. It's unlikely your children's classes will require all of them, so an a la carte approach would probably save you money. It's likely, for instance, that Adobe Photoshop would be all that the kids really need for a class like that.
And then, because it's a school, and financial reality is what it is, the school has probably rejected the expense of Photoshop in favor of GIMP, which is free, and which will run on your Macs.
If this is specifically being done with that elective course in mind, my first step would be to try to find out what software they're using in the classroom, and see if that's a good match for you at home.
