How I think Robin's Dick Grayson through Damian Wayne would be handled if they were in that Trilogy
He'd probably be 15 or 16, and Bruce wouldn't bring him into the field, at all. In fact I think he'd probably just mentor Dick and be his guardian, while Dick would train, skip being Robin, or at least being called Robin by anyone but Batman, Alfred, and Barbara, he'd probably just be Nightwing in a few years. I can imagine if he did have a few solo adventures as a kid he would:
1. Use his days in the circus for a plethora of his skills, such as Gymnastics, Parkour, and maybe even a few tricks learned from Batman.
2. If he had excellent accuracy with Batarangs, you could use the explanation that he'd learned dagger throwing from a friend of his parents while he was still in Hayley's Circus. Then maybe know a few martial arts tricks from Bruce but not have truly in-depth knowledge.
3. I could see him being Robin behind Bruce's back, and working with Barbara Gordon, who would take a more Oracle-esque role, Batman wouldn't allow her to be Batgirl at all. She's his friends daughter after all. He could take on people like Anarky, or
4. Then once he's Nightwing he could still be Batman's partner.
5. OR he could go the Officer Grayson route instead, that was a pretty cool idea from the old Nightwing comic.
Equipment: Shuriken, Eskrima Sticks or Bo-Staff(It would make a ton of sense when you're taking on five dudes at once.) Smoke Pellets, Grappling Gun/Hook, Taser, Night vision goggles.
Age Range: 16-
Nightwing Age Range: 19-
Costume: Young Justice costume(Robin), Young Justice(Nightwing) or New 52(Nightwing) or Pre-Flashpoint(Nightwing)
1. I doubt Bruce would make him Robin, he'd probably just be put in a boarding school for troubled youths.
2. Or he could experience a tragedy of his own and become Red Hood, maybe Talia would see something in him and take him under her wing, he'd be more willing to kill criminals anyway.
Age Range: Adult
1. Oracle like Position, until he's better trained.
2. He like Dick, could solve crimes on his own.
3. He could go be called Robin, but would probably just be thought of as another vigilante like Dick.
4. Or like in Arkham City, he could just be a cage fighter in his spare time.
Age range: 17-20 or older...
Equipment: Same as Dick's minus Eskrima sticks.
Costume: Red Robin or 2000s costume
1. He's a trained killer, nuff said.
2. Batman might take him with him, just to make sure he doesn't continue killing people.
Costume: Regular costume, only the green is all black instead.