Just thought someone might find this useful. For example if you need parent node to redirect it to the first child document dynamically, just include the code in Page_load().

string parentNodeAliasPath = (string)CMS.CMSHelper.CMSContext.CurrentPageInfo.NodeAliasPath.ToLower();
parentNodeAliasPath = parentNodeAliasPath.Trim() + "/%";

CMS.TreeEngine.TreeProvider tree = new CMS.TreeEngine.TreeProvider();
DataSet ds = tree.SelectNodes(CMS.CMSHelper.CMSContext.CurrentSiteName, parentNodeAliasPath, CMS.CMSHelper.CMSContext.CurrentDocument.DocumentCulture, false);

if (!CMS.GlobalHelper.DataHelper.DataSourceIsEmpty(ds))
{
// If child nodes exist
DataView dtView = ds.Tables[0].DefaultView;
dtView.Sort = "nodeOrder ASC";
string path = dtView[0]["NodeAliasPath"].ToString();
string resolvedURL = ResolveUrl(CMSContext.GetUrl(path));
Response.Redirect(resolvedURL);
}
else
{
//If child nodes do not exist do not redirect
}