Those are not the personalities those character are written with. Parenthood doesn't always bring maturity, going to a Trek or Comic Con can prove that. Hell, the subjects of debates we have on this board can prove it too.
Folk dress up like their favorite characters and their children too. Don't we do it because in part it's bring back a little bit of our inner child because we're playing pretend? It allows us to indulge our immaturity in an acceptable environment. It's a holodeck nothing more than a super advanced Playstation? So even Picard playing Dixon Hill is endulging his inner child by playing pretend.
I once dressed up as Spock for Halloween. And as for Tuvok being the so-called "only" adult on Voyager...well he IS a Vulcan and is much older than the rest of Janeway's crew, right?