You have 2 options when you save your movie.
If you use the default it will save it as a .WMV file but if you click on
the "Other Settings" radio button and then the arrow next to the dropdown
list you can then select "DV-AVI (NTSC)" from the list and save your movie
in the recommended DV-AVI format.
Here's where it will get tricky in your case however since you apparently
need to transfer the movie file to your sons computer. DV-AVI creates very
large files, transferring to your sons computer via email will be next to
impossible, so saving in a smaller lower quality .WMV file may be advisable
in your case.
I don't know how you plan to get the file(s) to his computer so I will now
skip to the part where you already somehow managed that task. Now your son
needs a DVD authoring program such as one of the many listed on my website
in the "DVD Programs" section:
http://www.remember-christopher.dostweb.com/Wojo's_Place/
You said your son has a CD burner which will work since these programs can
create what is called a VCD. A VCD is kind of like a mini DVD. It will play
on most DVD players but is lower quality than a DVD. But if your son
actually has a DVD burner and not just a CD burner then these programs will
also allow you to create a complete DVD with menus etc...
All the programs listed on my website have full working free trial versions
available with the exception of Nero's Nero Vision Express so you should be
up and running as soon as you manage to get the video to your sons computer.