I would go ahead and use a Global Entry kiosk. There's usually a question about commercial goods. If there's not, you could either 1) Tick the question that most closely matches what you have or 2) Make a verbal declaration to the nearest CBP officer.

Your bags will already be checked, so I would carry photographs of the items and as much information as possible about them, to minimise the risk of a physical inspection.

(This is assuming you have a through connection. If your goods are entering Canada then it gets a little more complicated.)