If there's one thing I love to build, it's wheels.
One thing I like to do with all my wheels, no matter how well they are designed, is to add a bit of putty to round off some of the straight edges.
I use a water based wood filler which bonds really well to paper, I water it down to make it easier to spread around. It can then be sanded for a smoother look, then painted. With my latest wheels, I mounted them on a dremel tool for sanding, it worked really well. I've added some pics of my Scud wheels to show what I mean.
Another tip I would add, for that kit you are building, would be to make the wheels a bit smaller in diameter, then add some strips of paper, wrapped around the tread, wider on the outside, narrower in the middle, to give it the rounded shape you want, then maybe smooth and sand before adding tread.
Treads can be cut from a thicker card and even just adding basic squares can add a lot to the 3D look of the model. If you don't want to have to paint the wheels, you can try printing multiple copies of the wheel parts to use layers for a more 3D look.