Exclude Paid Membership Pro My Account page and child pages from Yoast XML Sitemap

pmpro-exclude-pages-from-sitemap.php

<?php
add_filter( 'wpseo_exclude_from_sitemap_by_post_ids', 'pmpro_my_account_exclude', 10, 1 );
/**
 * Exclude page 'my-account' and child pages.
 *
 * @param array $excluded_ids The excluded post ids.
 * @return array Updated exlucded IDs.
 */
function pmpro_my_account_exclude( $excluded_ids = array() ) {
	$maybe_page_ids = wp_cache_get( 'pmpro_exclude_pages' );
	if ( $maybe_page_ids ) {
		return array_merge( $maybe_page_ids, $excluded_ids );
	}
	$page_ids = array();
	$page     = get_page_by_path( 'my-account' );
	if ( $page ) {
		$page_ids[] = $page->ID;
		$posts      = get_posts(
			array(
				'post_type'      => 'page',
				'post_status'    => 'publish',
				'post_parent'    => $page->ID,
				'posts_per_page' => 100, // modify this to account for the number of members.
			)
		);
		if ( $posts ) {
			foreach ( $posts as $post ) {
				$page_ids[]  = $post->ID;
				$child_args  = array(
					'post_type'      => 'page',
					'post_status'    => 'publish',
					'posts_per_page' => 100,
					'post_parent'    => $post->ID,
				);
				$child_posts = get_posts( $child_args );
				if ( $child_posts ) {
					foreach ( $child_posts as $child_post ) {
						$page_ids[] = $child_post->ID;
					}
				}
			}
		}
	}
	wp_cache_set( 'pmpro_exclude_pages', $page_ids );
	return array_merge( $page_ids, $excluded_ids );
}

Tweak https://gist.github.com/ronalfy/031ab5aeb00c025e7049e363ca8c2ca4#file-pmpro-exclude-pages-from-sitemap-php-L23 for how many members to process. Will be slower the more members are excluded.