Non sono sicuro di avere capito bene il problema.

Comunque.

codice:
var span; var clone; var id;
window.onload = function(){
 id = document.getElementsByClassName('padre')[0];
 var b = document.body;
 id.addEventListener("dragstart", dragStart, false);
 id.addEventListener("dragend", dragEnd, false);
 b.addEventListener('drop', function(event){dropp(event)}, false);
}
function dragStart(){
 //span = document.getElementsByClassName('padre')[0];
    span = this;
 //clone = span.cloneNode(true);
}
function dragEnd(){
 //if(document.getSelection){
 // range = window.getSelection().getRangeAt(0);
 // range.insertNode(clone);
 //}
}
function dropp(e){
 e.preventDefault();
 range = window.getSelection().getRangeAt(0);
 range.insertNode(span);  
}