Well I would say it depends on the focus of your series. I assume it like this since we are talking about a second part, so it is not ruled out that there is a third, fourth, etc.
Let's see how I can explain it. For example, suppose you have a series in which the MC is Indiana Jones, in that case you are fried, the audience throws objects on stage, expresses their discontent, the author escapes.
On the contrary, it is different if we have a river type novel where a character does one thing; another runs parallel to the story apart from him and they eventually cross paths. I mean, I know there are river novels where anyway the common thread is carried by a single MC. A classic example is Dune. But, continuing along the same lines, the same Star Wars and the way it is raised allows any character to have their own story; that is, the narrative weight does not rest on a single character.
So, as you're telling me, the first thing that comes to mind is a case of doppelgänger. Not in the sense of the perfect opposite; but yes in the fact that you are going to make a castling.
Second problem. Potential, yes, only you are clear about that. But, if your novel is YA, and you make that change you say, the boys go to get their baseball bats. That's why the doppelgänger thing. It would be a harmless substitution, except that adolescent / adult implies a generation gap and statistically people always bet the silver on the youngest.
Except, except that the adult has not another alternative. Only something like that could stop people from throwing eggs and tomatoes at you. Let's say that there is such a catastrophe that not even the cat is saved, and this poor adult, who is old and tired, seeing that only he can fix things immediately produces identification in the reader. Damn, very bad person, that screenwriter. Otherwise I find it difficult for them to buy your story, unless you had Liam Neeson.
By the way, could you give a plot synopsis? I believe that with more antecedents we can look for the turn.
