Isla de Mezcala is a little more than an hour from Guadalajara, or, at least, getting to where you take the boat is that long. Here's Jalisco's official webpage about it. And here is a nice long thing about its history. It looks like this is a good place for families to visit since it involves boats and ruins and a prison. And a church, of course.
Here and here and here are some blog posts from people who've been there. The second isn't very useful since it's mostly about the people who visited rather than what was visited, but what can you expect from a blog?