Obscure cartoon film where a man squats on his porch while smoking a pipe

I know this movie exists. My family thinks I’m insane. I’ve been looking off and on for about two years – I have to find it, at least before I die.
1) A color CARTOON film, probably made in the 80s or 90s. A family goes on a vacation to an island. The movie was probably for children.
2) The main character was likely a young blonde boy. For some reason, he wants a magic stone. At one point, the stone rolls down this slide inside a mountain, and he jumps down the slide with it – they both end up coming out of a hole in the side of the mountain.
3) I think I remember the antagonist of the film being a pterodactyl.

4) MOST IMPORTANT DETAIL: There is a scene where the father in the movie goes out onto his porch, puts a pipe in his mouth to smoke, and begins squatting. Every time he squats, smoke puffs out of the pipe. He keeps squatting until eventually, the entire front porch and screen is covered in dark gray smoke. I remember this scene vividly, and I just have to know what it’s from.

People have suggested Fern Gully, but that’s definitely not it. I’ve looked through so many movie lists, so this movie must have been pretty obscure! I know I watched it on VHS. Thanks.