Parent page using wp_dropdown_pages and multiple post types

wp_dropdown_pages() does not accept a post type as an argument, however, as noted in the Codex, it may be possible to use some arguments of get_pages() like post_type.

Unfortunately, the post_type argument for get_pages() only accepts a string and not an array of post types.

Although you may be able to pass a single post type as an argument to wp_dropdown_pages() you cannot pass an array of post types.