IANAL. but on my reading of the law it appears that it is.
1. Illegal to possess a handgun under 18, with a few exceptions.
2. Illegal to purchase a handgun from an FFL until you are 21.
You could try to get a purchase permit from the sheriff, but that is very hard under 21. Basically, the 18-21 age is not covered by NC law as far as possession. That which is not illegal, is legal. So it looks to be legal to possess, but you cannot purchase or own it yet.
Make sure you know your laws. Depending on how young you look, you may get some extra attention. As far as GATTTOTP, a holstered handgun is not considered threatening someone. Though some LEO's will still try to use that law against an OC'er. I have had several interactions with LEO's while OC'ing and everything has been fine.
Actually, the knife may be the tricky part. Cities and towns can restrict knives far more than they can firearms. You may want to check the ordinances in the area you are carrying it in. Here is a website, if your area is not on the site you would need to contact city hall for the ordinances.