How Every Robin Can Appear In The Batman 2
2. A More Responsible Batman
Bringing in Robin has the unsavoury aspect of child endangerment. While easily glossed over in comics, it isn't a good look in a big screen adaptation. Likewise, aging the sidekick up tends to come off as awkward and forced.
One option is to lean into it. The Batman was never afraid to wear the weirdness on it's sleeve. Matt Reeves could put the unhealthy aspect of Batman indoctrinating a child into a dangerous lifestyle on the front page. But presenting Batman as a child abuser would make him a lot less likable, as evidenced by "All Star Batman And Robin The Boy Wonder" - a book which is infamous for (among other things) the Dark Knight's abusive treatment of Dick Grayson.
If a Batman-inspired gang of teens begins fighting crime on their own, Bruce is the more responsible party for taking them under his wing. Rather than putting minors in danger, he is taking charge of minors who choose to put themselves in danger and providing them with training, supervision and rules. Interestingly, this exact thing happens in "The Dark Knight Returns". The Robins in "We Are Robin" are similar to DKR's Sons of Batman, and it would make perfect sense for a movie adaptation to blend elements of both.
This also presents the opportunity to do the one thing Batman films love to do; shamelessly borrow from "The Dark Knight Returns". Imagine Batman on horseback, leading an army of youths through a city in chaos., but this time they wear Robin's colors.