I guess since the pixels aren’t necessarily permanently mounted to the the board maybe not necessary to include the pixel type.
I made this smallish knob you could 3d print that might work.
Or I could model an even more slender one for you if you’d like.
Thanks again to Marc, Paul, and Ken for all of the help and suggestions here! I placed the order with OSH Park (along with a couple of purple Teensy LCs) this morning in time for the Super Swift service, so hopefully I’ll have them this weekend.
@Jason_Coon - You might want to consider including three female headers, three male headers and three long male/female jumper cables in your kit. With the female headers soldered into the PCB where you would connect the NeoPixel stick to, you could either plug the NeoPixel stick that has male headers on the input end into the female headers directly on the PCB or connect the NeoPixel stick to the jumper cables and then to the PCB. This is what I have done with my NeoPixel sticks and it allows you have different orientations for the NeoPixel stick. This allows you to switch easily to other RGB LED products like a NeoPixel ring, too.
Also, you might want to consider two different products in the future. One product would include your PCB and another product would include a long breadboard.
Finally, your kit is reminding me a lot of some of the old Allied Radio Knight Kits. Building some of those kits got me started in electronics along with Popular Electronics magazine.
@Ken_White Thanks again for the suggestions! The components should arrive from Digi-Key today, and the PCBs Monday, so I’ll get them assembled and tested then.
It’s alive! 
More info, PCB files, parts list, code, etc: https://evilgeniuslabs.org/fastled-rgb-hsv-tutorial
missing/deleted image from Google+
Awesome! So cool.