This looks amazing! just seeing these characters brings back memories. Not to mention how great they all look, though there was one i remember. Arnold's friend's older brother, he had a girlfriend that might fit into the story.
however with how great it looks i have an issue. playing as the grandpa(phil)? if we had our own character, a mc we could change ourselves or something else like a faceless protag i would jump in no problem. as it is, as much as i want to and while i may try it later. i can't really find playing as a old man fun.
I do wish you the best and hope everything goes well. again this game looks fantastic and shows promise.