I think you've got a great collection of fabrics that will work together no matter how they fall. The fine tuning and second guessing can stick with us forever...
When I'm looking at what happens to scale, I'll cut out the center of a piece of colored paper (junk mail, etc) the size of the finished block and just move it randomly over the fabric to see what happens. I'm thinking if you have about a 6" block the trees will be fine, but see what the worst possible placement is and whether you can live with it just ending up cutting that way or not.
In fine tuning, if you are keeping the colors together, I'd put the ivy on black print between the large scale cardinal and sweaters & stuff prints. Or maybe move the white background Cardinal in-between the red snowman and flower fabrics.
But again, this sort of fussing is the sort of thing that takes me hours and days to decide. And by the time I'm done with the project I always know if I had only done this or that, it would be better.