This quick block of Javascript will allow you to disable keyboard input within Date fields. This snippet is helpful if you need to avoid the virtual keyboard from appearing within the datepicker.
<script type="text/javascript">
gform.addFilter( 'gform_datepicker_options_pre_init', function( optionsObj, formId, fieldId ) {
jQuery( ".datepicker" ).attr('readonly','readonly');
return optionsObj;
});
</script>