So to start off, I would assume that the first major hints and winks at the bat-family would be made in BvS:DoJ. How this would work is when we see Batman for the first couple of times, he is researching Superman, learning as much as he can about Kal-el. Just doing his everyday detective work, being batman and all. While he is doing this, alfred informs to bruce, "your son has been sent to master Richards as you requested, sir" that right there would set up Damian Wayne and Dick Grayson. Bruce says, "Good, the last thing I need is him trying to take down an invincible alien" as he gets up and walks past the Glass cases holding all of the Family suites, Batman's newest suit, Nightwing, Damian's robin suit, Jason's red hood, Tim drakes Red Robin suit, Barbara's batgirl, and finally the Batman Beyond suit to hint at future movie possibilities... And all fonboys and girls would love this clip because it is something that everyone has always loved. The suits. This also sets a display for who is part of the bat-family.
As the camera pans away you see this massive outstretched view of how really big the bat cave is, with multiple batmobiles in frame (maybe some of the original batmobiles from the past movies) making a nod to the batmen of the past. Batman gets into the batmobiles that we have seen in the photos with Ben Affleck, and speeds out if the cave. Batman talks to Alfred from a speaker in the car about going to metropolis and that he doesn't intend to confront superman until he knows for sure his weakness. After he gets done talking to Alfred he calls Nightwing, you actually see Nightwing in the film.The first thing he says to batman is, "I know a lot has happened, but it doesn't change anything (meaning his frustration with batman when he quit being robin) and you leaving me to baby sit doesn't help" in this frame you can see Damian in the background looking pissed and giving Nightwing a ugly look. Batman snaps at Nightwing, saying he doesn't have time for his complaining and tells him that he and Damian need to watch over Gotham while he is gone and that Nightwing should know that he wouldn't let just anybody watch over the city. Of course Nightwing pipes down and and agrees in disbelief. They stop talking and Nightwing turns to Damian and simply says, "get your suit, its time for some fun." Damian replies with, "Hell yeah!" As it cuts back to batman.
This scene could set up a potential Nightwing spinoff movie that could include Damian Wayne as robin for a costar role. Just that small amount of screen time could set up a whole new batman universe, throughout the movie batman could check in on Nightwing where they mention Tim drake as Red Robin, Jason Todd as Red Hood or Barbara Gordon as Batgirl. This could work really well. If Warner Bros. And DC play their cards right there could easily be a huge universe that can be made, even bigger if they combine with the TV universe. I hope this can be a good inspiration for people, because DC has so much to offer aside from batman and Superman. The side kicks are amazing. It would be awesome to see a Batgirl and Supergirl team up movie, that would attract a lot of fangirls and fanboys. I hope the future is bright for DC.