main menu items with children are not linked

Open Atrium uses a mobile-friendly "tap interface" for menus using the Bootstrap CSS framework. So yes, clicking on the parent item just toggles the submenu and does not go to the specific link in the main menu because on a mobile device there would be no way to open the submenu otherwise.

If you are just creating a desktop site you can go into the Admin -> Open Atrium -> Config page and in the Toolbar vertical tab you can enable the Mouse Over checkbox. This will enable mouse-over and has the side affect of allowing you to click on parent menus items. I know this works for normal toolbar widgets but haven't specifically tried it with the Main Menu since that's a drupal core menu block.