Don't block characters' paths, unless it makes sense in the story. Even then don't overdo it. If they follow the path you had in mind - that's perfect. If they decide to follow their own path - support that, unless it breaks up the plot or makes no sense.
They want to investigate the forest before going into the cave? That's fine - even if you don't have anything about that forest - e.g. you only thought of it as part of your scenery. Just go with it, play around with the situation. Maybe migrate the party's goal from the cave to the forest (their intel may have been wrong or the goal may have moved). If there's a plausible explanation - go with it. Be flexible.