Newb teen first time flying kit help

Here's the scoop. I work in the mental health field and am continuously looking for hobbies to get some of the kids I work with involved in. I know there are many hobbies out there, but there aren't so many that have the criteria I'm looking for.

Basically I need points covered. 1-It's exciting enough to get a child/teen suffering from a mental ailment (ex depression) involved in. 2-It's something that takes work to achieve. (Track for example may take skill to master, but doesn't take skill to accomplish on a base level.)

I want the client to put in effort and get results. 3-It's a hobby that takes work to master. 4-It's something that has continuous room for growth. With all that in mind, I've spent some time researching RC planes.

Some background here. I've never flown a plane or drown. The most I've done was some rc toy helicopters. I also am ok with my hands-not amazing.

The client here is a 14 year old child without experience in rc or flying. He's very good with building projects in general and enjoys a good puzzle. Here's my question(s): 1-Since I don't want to just give him a rtf plane, what can you recommend. I don't want it to be too difficult as he will lose interest while building it. I've seen some diy ideas like for example this

https://www.rcgroups.com/forums/showthread.php?2886889-Learn-to-Fly-with-a-DIY-Plane-under-100!-(Flight-Pics-too!-and-now-Flight-Videos!)

Another option I came across was this https://store.flitetest.com/tiny-trainer-get-started-package/

Also, what other supplies would I have to purchase? Last question, besides forums and the like, is there any book you can recomend for a such a child to learn about rc without being too detailed as to bore him?