JQuery Show/Hide UL children and unselect other parents checkbox

I'm going to do my best to describe my problem. This community has helped me before, so I'm hoping someone will be kind enough to lend me their help once again. I don't really know much about JQuery.

We're setting up a wordpress site using Easy Digital Downloads, because of that we have some restrictions, like not being able to change the HTML, but we can add add JQuery elements on a page.

This is for a category selection system where a user should be able to select only 1 parent category and multiple sub categories under that parent.

I'm looking for a JQuery solution for the following scenario.

We have 5, potentially 6, "categories". These categories have sub categories represented by a UL. By default the sub categories should be hidden. When you click a parent category it should display the sub categories below. If you at any point click the same parent category, it should unselect all children and hide them again.

I also only want 1 parent category to be selected at any given point.

Let me give you a scenario. You click on Cat A, it expands and shows 4 sub categories. You click 2 of those sub categories. You change your mind and instead click on Cat B. This should then hide the sub categories of Cat A and unselect the children, as well as the parent of Cat A.

Just if I haven't made it clear enough, it's important that you can never select a sub category without a parent category.

I've made a basic fiddle with something I found in another thread. Just is just for showing and hiding (though I haven't added a class for hiding yet) This has the html structure we're using.

Another issue is that all of the parent categories use the same class for the children (.children)

$('#in-download_category-156').click(function() {
  $(".children").toggle(this.checked);
});

FIDDLE

I know this is a big ask, so I appreciate any help you can throw my way! Thank you