controller.js

isValid: Ember.computed('emergencyContactsAreAvlid', 'allAttendingConsentsAreValid', function(){
    var promises = [];

    var ePromise = this.get('emergencyContactsAreValid');
    promises.push(ePromise);

    var cPromise = this.get('allAttendingConsentsAreValid').then(function(result){
      return result;
    });
    promises.push(cPromise);

    return Ember.RSVP.all(promises).then((results) => {
      var rtn = true;
      results.forEach((result) => {
        if(!result){
          rtn = false;
        }
      });

      return false;
    });
  }),

  emergencyContactsAreValid: Ember.computed('parents.@each.emergencyContact', function(){
    var parents = this.get('parents');

    var count = 0;
    parents.forEach((parent) => {
      if(parent.get('emergencyContact')){
        count++;
      }
    });

    if(count > 2){
      return true;
    } else {
      return false;
    }
  }),

  allAttendingConsentsAreValid: Ember.computed('parents', 'students', function(){
    var self = this;

    var parents = this.get('parents');
    var students = this.get('students');

    var subItems = [];

    parents.forEach((parent) => {
      if(parent.get('groupRequestHasUsers').get('length') > 0){
        var promise = this.store.query('user-has-contract', {user_id: parent.get('id'), with: 'all'}).then(function (data) {
          var that = self;
          var contractExists = false;
          data.forEach((userContract) => {
            if (userContract.get('contract.code') === 'Consent') {
              contractExists = true;
            }
          });

          return contractExists;
        });

        subItems.push(promise);
      }
    });

    students.forEach((student) => {
      var promise = this.store.query('user-has-contract', {user_id: student.get('id'), with: 'all'}).then(function (data) {
        var that = self;

        var contractExists = false;
        data.forEach(function (userContract) {
          if (userContract.get('contract.code') === 'Consent') {
            contractExists = true;
          }
        });

        return contractExists;
      });

      subItems.push(promise);
    });

    return Ember.RSVP.all(subItems).then((results) => {
      var rtn = true;
      results.forEach((result) => {
        if(!result){
          rtn = false;
        }
      });

      return rtn;
    });
  })

template.hbs

{{#unless isValid}}

{{/unless}}