as far as facial expressions go, the characters do get more expressive down the line, but its extremely subtle. I found the lack of facial expressions a little jarring on my first readthrough, until I got to about day 10-12, now I really like that aspect.
I think Cosy Cafe is a pretty unique looking VN, and the way characters faces are treated is a large part of that. As CyBeRd0g said the focus is much more on the eyes than on the mouths of the characters.
Depending on where you are, you might have already noticed how the girls tend to look down sometimes whenever there is an emotional moment, when usually they look up at the MC.
This happens fairly often, and I think its used to great effect. Once you shift your focus from the girls mouths to their eyes, you will probably not mind the lack of mouth movement so much.
Another reason I like the subtle facial expressions is that it allows the writing (and by extension my imagination) to do most of the heavy lifting. Its a bit hard to explain, but I like when the narrator adds flavour to the render, allowing my mind to flesh the scene out in my head.