Well, Pixar's never let me down, personally, but I think they took a risk this time with having a geriatric main character. Do kids want to see that?
Maybe Disney is capitalizing on kids associating going to Grandpa's house with receiving envelopes of money.
Actually, the whole thing feels like a Westernized version of a Miyazaki film, which makes me want to see it even more. I always felt there was some sort of cultural gap with Studio Ghibli films that made it hard for a Westerner like myself to fully embrace. They looked cool, but I always felt like I was missing something. Like the plot in Princess Mononoke.