Yes, there will be a Dave route. (And more others! ;)). Gran is like the main mascot of the VN but right now, the MC isn't exactly on any route specifically, just 'testing the water' so to say. Later on, the player gets to decide who they'd like to spend more time with (Atleast that's what I have in my head.). I'd say more, but I don't want to spoil the story out just yet.
Thanks for playing, cheers.
-D