Get child count from rapidxml:xmlnode to get random child node

I can turn my XML document file into rapidxml object:

if(exists("generators.xml")) { //http://ift.tt/15Ycuzn
    rapidxml::file<> xmlFile("generators.xml"); // Open file, default template is char

    xml_document<> doc;               // character type defaults to char
    doc.parse<0>(xmlFile.data());;    // 0 means default parse flags
    xml_node<> *main = doc.first_node();  //Get the main node that contains everything
    cout << "Name of my first node is: " << doc.first_node()->name() << "\n";

    if(main!=NULL) {
        //Get random child node?
    }
}

I'd like to pick one random child node from the main object. My XML looks like this (version with comments):

<?xml version="1.0" encoding="windows-1250"?>
<Stripes>
  <Generator>
     <stripe h="0,360" s="255,255" l="50,80" width="10,20" />
  </Generator>
  <Generator>
     <loop>
       <stripe h="0,360" s="255,255" l="50,80" width="10,20" />
       <stripe h="0,360" s="255,255" l="0,0" width="10,20" />
     </loop>
  </Generator>
</Stripes>

I want to pick random <Generator> entry. I think getting the child count would be a way to do it:

//Fictional code - **all** methods are fictional!
unsigned int count = node->child_count();
//In real code, `rand` is not a good way to get anything random
xmlnode<> *child = node->childAt(rand(0, count));

How can I gild count and child at offset from rapidxml node?