Capability parameter of add_submenu_page() function can only take a single capability, so if you are using the built in roles you can select a capability fro the long list that both administrators and editors have any of these (use any of these freely):

• moderate_comments
• manage_categories
• manage_links
• unfiltered_html
• edit_others_posts
• edit_pages
• edit_others_pages
• edit_published_pages
• publish_pages
• delete_pages
• delete_others_pages
• delete_published_pages
• delete_others_posts
• delete_private_posts
• edit_private_posts
• read_private_posts
• delete_private_pages
• edit_private_pages
• read_private_pages