He should have no problem getting it on the ship, but DO NOT try to bring any back. Customs randomly searches people as you get off the ship re-entering the US. Be careful & only bring what he'll use while there. There is no search getting on the ship, the airport if he flies to the port will be the only worry. Most cruise lines take your luggae from you & put it in your cabin, but they give you the option to do it yourself. I always do, becuase it takes them several hours to finally deliver your stuff anyway. They may be screeing some of the bags then, who knows.
I've travelled with preloaded pins stuffed into those toothbrush cases with padding on stuffed in the ends so it wont push the plunger. I'm sure you could still get pinched if searched, but they are not looking for AAS in those searches.
Bottom line: bring only what you need & dump any leftovers on the ship.