'post', 'posts_per_page' => 3, 'meta_query' => array(
'relation' => 'OR',
array(
'key' => '_sn_primary_checkbox',
'value' => false,
'type' => 'BOOLEAN'
),
array(
'key' => '_sn_primary_checkbox',
'compare' => 'NOT EXISTS'
)
));
$myposts = get_posts( $args );
foreach( $myposts as $post ) : setup_postdata($post); ?>