I have only ever made one breadboard end table. I basically cut a tongue the full length of the table top with a Stanley rabbet plane. You could use a router no problem, I'd think. Then I used a variety of handsaws to cut the tenons from that tongue - regular tenon saw for the sides of the tenons, then a coping saw to remove the waste between the tenons. Chisel to clean up the corners. It worked fine, and really wasn't too difficult.
Mortise by whatever method you're comfortable with, leaving the exterior mortises oversized by maybe 1/8" on either side of the tenon.
I then secured the breadboard with dowels through the breadboard end and tenons. Slotted holes in the tenons on the outside.