Hi,
I have found out how many fittings you will need for you Son's build. With the amount of parts he has he will need 22 fittings but I would recommend getting at least an extra one as you will need it to fill up the computer. I have left a link for 2 types of fittings that I think would suit him the best for his system.
Monsoon (Normal) Fittings :
http://www.performance-pcs.com/monsoon-free-center-compression-fittings-3-8-x-1-2-single-matte-black.html
Monsoon (Chaingun) Fittings :
http://www.performance-pcs.com/monsoon-chain-gun-compression-fittings-3-8-x-1-2-single-chrome.html
(I'am sorry if you find this cheaper somewhere else, I'am from England so I'am not used to buying/searching up parts from US websites)
You can buy these fittings as individual components or as a six-pack. They range from $7-$8 each and are one of the cheaper options to go for.
For tubing, he will need to get some 3/8" (Inner diameter) and 1/2" (Outer diameter), here is a link to some:
http://www.performance-pcs.com/primoflex-b-advanced-lrt-b-tubing-3-8in-id-x-1-2in-od-crystal-clear.html#Specifications The price for this is price per feet, so 12 inches or 30cm.
I hope this helped you and if you need assistance again, contact me and I will do what I can.
Thanks,
Simon