How can my DS put together a great portfolio instead of sending in test scores?

My DS is a junior and looking at CS, with WPI his number 1 choice. He has an UW GPA of 3.85 WGPA of 4.4 in all honors courses from a very competitive HS. Next year he will take 2 AP courses and 3 Honors courses. EC include coordinator of the FIRST robotic software team, Mandarin Club, volunteers for a foodbank and is a blackbelt in Karate where he teaches other students. His SAT scores are low despite studying Math 620 Writing/Reading 590. He wants to use the flex option instead of sending his SATs. How would he present all of the coding he has done for different projects that he has done for school or for projects he has developed himself? Would he send on a CD with a summary of each? How does this work? Also, what do you think his chances are of getting in with the above profile? He is a self starter, extremely motivated and loves computer science (he gets excited looking at the course requirements and electives!)

Yes. That sounds reasonable. There is a form for documenting your work if you’re applying using flex path as opposed to a standardized test:
https://web.wpi.edu/Images/CMS/Undergraduate/WPI_Flex_Path_Form.pdf

You can contact admissions to check what format they would prefer: a CD, a flash drive, web site, or something else.