I have a modest amount of expertise in this area.
So not knowing what Jr. already has, here's a few recommendations.
Nail clippers on a lanyard. Great for clipping lines and having it hang around your neck saves time trying to dig it out of your pocket or tackle box.
Hemostats. I prefer the offset ones. They make removing a hook from a fish a breeze. The offset ones make it easier to see what you are doing.
Needle nose pliers. Same use as hemostats but for larger size hooks.
Fishing vest. They have lots of pockets to carry stuff. A must for fly fishing. It allows you to fish and move without having to haul by hand a bunch of boxes.
Lures. A handful of mepps spinners can make for a productive day on the water. Many different species of fish will attack a spinner. Silver and gold are good color choices. #2 & #3s are the right size for Maryland fishing.
Polarized sun glasses. First they are for safety to prevent getting a hook in the eye. They also let you see below the water surface.
If you think he'd like to fly fish then there are fly fishing starter kits that include the pole, reel and line all together. If you have deep pockets you could get him a charter or guided fishing excursion.
Other useful items include a landing net, filet knife, hook sharpener or some other fishing gadget. You could ask the people he fishes with if he's mentioned any gear he'd like to have.