Should be page 143 on the Yaktribe comprehensive rulebook.
Ctrl+F "Advancements at the start of a battle" if you're unable to find it, and it should bring you directly to that section.
Worth knowing that Delaque are getting a new book (next month?) so it's possible that your son's list will be a smidge outdated soon... That is assuming you are using the "house of" books for the gangs, rather than merely their rules in the Comprehensive Rulebooks. (I'd recommend going with the "house of" books, as they're FAR better than the basic rules contained within the core book, and they also have unique mechanics/skill trees for the relevant gang ... Not that I would ever advocate such a thing, but I have heard that all of them (except House Of Faith for Cawdor) are pretty easy to locate as PDFs online.)
Also: Thematically I might suggest playing Enforcers rather than Orlocks, if you're to be the arbitrator, though I'm a little Biased as they're my current gang.
With regards to 3D terrain:
https://ttcombat.com/ makes a range of lasercut MDF terrain that's really rather good for Necromunda. Very reasonable pricing for the amount you get, as well.
If you have any other questions please don't hesitate to ask.