Query multiple post types, but different order for each

I have a query which searches 2 post types as below:

$args = array(
    'post_type'              = ['post', 'promotion'],
    'posts_per_page'         = 12,
    'paged'                  = $paged,
    's'                      = isset($_GET['search']) ? $_GET['search'] : '',
);

This orders them by default, by published date.

I need to add a third post type events. This however needs to be sorted by a custom field event_date asc and to disregard those which the event_date is in the past. Does anyone have any suggestions on how this could be done? While keeping the pagination and search.

Thanks in advance

F