They would have been more appropriate and more effective invitees but Trump didn't think of them when he tweeted is reaction to Cuban. Lost opportunity.
Hillary wouldn’t be disturbed by them for sure, plus no one else would know who they were so it would have virtually no impact.
Trump may have other guests at the debate like the mother of Sean Smith or the father of Ty Woods. It could be one of the surprises that Giuliani mentioned there would be.