Complex selection and checkboxes

I have a complex nested form, without individual classes (can´t change anything there...) and want to check all child checkboxes.

Because of the structure I´ve to do something like the following js:

$('.selector input').click(function(event) {
        if(this.checked) { 
            $(this).parents('.row').next('.checkboxselect').css( "background-color", "red" );
         }
        ...

That work fine so far, the area I need got the background color.

Now I need to check all checkboxes that can be found in .checkboxselect area, but have no clue how to do that... Maybe someone had an idea... Thx a lot! Best, Chris