As a friendly, I think we can do whatever we want. Probably are contractual obligations to field a competitive side, but I hope they don't include Villa and Pirlo.
I'm not sure if this is the case or not. You can certainly field trialists in friendlies but usually those trialists will be free agents. I'm aware of trialists playing friendlies while still on the books of another club (not talking in the US, here) but only when they're pretty much on amateur contracts playing for a move to a professional team, and I think amateur papers are far less restrictive. I think to play Wilmington players, who are not amateurs, we would essentially have to officially loan them in, and is the loan window open in the US right now?
All of this is a moot point, however, since I'm sure they wouldn't be going through with the match if they didn't have the squad, even if it meant paying a cancellation fee. I'm sure they reckon they have the players, regardless of whether it actually ends up backfiring on us of not.