Here is a link to a quilt I made where the binding finishes at 7/16 inch wide.
I just make a wider seam when I attach it to the quilt.
Jungle Animals Baby Quilt
Also - when sewing a wider binding to the quilt - look at this tutorial -
Stop Stitching Here - - -
I trim the batting even with the quilt - I also sew the top, bottom, and batting together - and I baste the binding edges together - it's extra sewing, but when putting the binding on, i feel like I'm only dealing with two edges instead of five.
If I had points along the edge, I would cut the batting and backing so that there would be enough batting to accommodate the binding.