Just in case someone else (like me) happens upon this thread looking for guidance, but doesn’t quite grok what José is suggesting (also like me, initially):
I happened to find this great TIL repo by @slashdotdash that gives you a working example:
https://github.com/slashdotdash/til/blob/master/elixir/dynamic-supervisor-start-children.md
Thank you, everyone! 
