ImageMagick - Scale and Fade Variable Height Images

Question

I'm a bit overwhelmed by all the options of ImageMagick, so I'm looking for some guidance whether what I am trying to do is possible.

I have a folder full of png images. Each image is a different size. I would like to:

1. Scale the images to a fixed width say 200px, allowing the vertical size to remain variable. For this, I know I can use "convert -resize 200"

2. Fade the bottom of the images to fully transparent. So the bottom 50px or so would fade from 0 transparency to fully transparent to the edge.

Is this possible using ImageMagick? Any tips on where I could look, or how this may be done?

Thanks