Tour.php (condensed)
class Tour extends Page {

...
   
   static $has_many = array(
      'TourDates' => 'TourDate'
   );
   
   function TourDatesFiltered() {
      return $this->getComponents("TourDates", "TourID=$this->ID");
   }
   
   function getCMSFields() {
      $fields = parent::getCMSFields();
      
      $tourDateField = new HasManyComplexTableField(
         $this,
         'TourDatesFiltered',
         'TourDate',
         array(
            'StartDate' => 'Start Date',
            'EndDate' => 'End Date',
            'AvailableSeats' => 'Available Seats'
         ),
         'getCMSFields_forPopup'
      );
      $tourDateField->setParentClass('Tour');

$fields->addFieldToTab( 'Root.Content.TourDates', $tourDateField );
}
....

TourDate.php (Full)
class TourDate extends DataObject {

static $db = array(
'StartDate' => 'Date',
    'EndDate' => 'Date',
    'AvailableSeats' => 'Int'
);

static $has_one = array(
'Tour' => 'Tour'
);

function getCMSFields_forPopup() {
$fields = new FieldSet();
$fields->push( new CalendarDateField( 'StartDate', 'Start Date' ) );
    $fields->push( new CalendarDateField( 'EndDate', 'Start Date' ) );
    $fields->push( new NumericField( 'AvailableSeats', 'Available Seats Left' ) );
return $fields;
}

}

1. I don't want the user to have to do this. I want them to be able to enter the new TourDate and have it associated with that Tour when saved

2. The filter obviously isn't working, and I should have realized this when the TourDates were set to zero. All Tour Dates are available for all Tours, but if they are selected in Tour1, they are un-selectable in Tour2. I want them not to show at all.