I’m not sure if this will work with get_posts(), you may need to switch to WP_Query https://codex.wordpress.org/Class_Reference/WP_Query, if you do you’ll need to change numberposts
to posts_per_page
$args = array(
'numberposts' => -1,
'post_type' => 'events',
'meta_query' => array(
array(
'key' => 'display_on_upcoming_events',
'value' => '1',
'compare' => '=='
),
'date_clause' => array(
'key' => 'event_start_date',
'compare' => 'EXISTS'
),
),
'orderby' => array('date_clause' => 'ASC'),
);