Mayhan,
Because you can have multiple employees on your lunch, you cannot put the employees as attribute on the page. This is only possible if the association would be 1-1. To be able to modify you employees on the lunch, you can try the datagrid or list-view widget.
See also: https://docs.mendix.com/refguide/associations and https://docs.mendix.com/refguide/reference-selector