There's a million threads that question how Dan Bongs work for humanoids, but this is a (hopefully) simpler question for non-humanoids.
My Eidolon has the serpentine type, and as such uses her tail for her grapple checks. She doesn't have exotic weapon proficiency with Dan Bongs, but she's not using them to attack. So, would carrying one of these give her the +2 to grapple or would it entail penalties?