Ooh, we're at Ares already? Well, speaking of him (unfortunately, I too speak from experience) he's not the nicest god you'll ever meet. He's usually harsh to his children as well! (Unless he's in a really GOOD mood). Mars is much, much nicer, and he sort of deserves respect, but his Greek form is just... blech! But he has some amazing powers, and his children [sometimes] inherit them. Here we go!
Weaponry: Ares and Mars children alike are uniquely skilled with violence, weaponry, bullying, and stuff of that sort. They just have a natural sense of dealing with weapons.
The Blessing of Ares: Ares kids, occasionally, during battle, receive the Blessing of Ares (Mars, whatever). The known ones are Clarisse La Rue, who was seen to have a fiery red aura around her during the Second Titan War, and Frank Zhang, the son of Mars.
Enhanced Abilities: Of course, like all demigods, Ares kids also have enhanced abilities.
Sense of War: I didn't know what to call this, but sometimes similar to Athena kids, they have a great knowledge of war strategies, so Ares kids make terrific generals.