Hi Simone!
I' just "discovered" this thread! Wonderful-wonderful work!!
The beauty of minimalism! Just simple yet so powerful! Bravo!
A technical thought:
I think one thing you could do, is keep doing your originals the way you do them, but not to use their scans for reproductions. If you only have 3 colors, that means that you need three color printing. and since all your shapes are vector )clean lines, flat colors, no gradients), you can just streamline the shapes, and give them in the copmuter any color you want.
Do I make sense? Then your files also will be lighter, only I don't know what software you use, and all that...
Still thoug, you can do smaller editions with three colors, and you could have very interesting results... It's definitely worth experimenting and investigating teh issue with printers, even small local ones. Just show it to them, and ask them what they suggest...
Good luck!