I've done this already on another piece with my router.  It took multiple passes.  First ½" wide and ½" deep.  Worked fine.

My concern is this knot. 

The table saw idea would work if the rabbet went all the way, but it stops short 5 3/4 from each end.  These boards are 92.5" long and 5 3/4" wide and 1.24 inches thick.

I'm thinking a new 3/4" bidirectional carbide spiral bit, multiple passes,might trim the knot without breaking it out.