There's other ways to disable the enter-key-submission.
function checkKey( e )
var kc = ( e ) ? e.which : event.keyCode;
return ( kc != 13 );
<form ... onkeypress="return checkKey()" ... >
Or, include a confirmation in your validation script at the end
return confirm( "Are you ready to submit?" );
use JS as a backup, and let HTML do the important work.