code: public void getChildren(
          final CmsUUID entryId,
          final boolean setOpen,
          final boolean continueIfParentNotLoaded,
          final AsyncCallback<CmsClientSitemapEntry> callback) {
  
          CmsRpcAction<CmsClientSitemapEntry> getChildrenAction = new CmsRpcAction<CmsClientSitemapEntry>() {
  
              /**
              * @see org.opencms.gwt.client.rpc.CmsRpcAction#execute()
              */
              @Override
              public void execute() {
  
                  // Make the call to the sitemap service
                  start(500, false);
                  // loading grand children as well
                  getService().getChildren(getEntryPoint(), entryId, 2, this);
              }
  
              /**
              * @see org.opencms.gwt.client.rpc.CmsRpcAction#onResponse(java.lang.Object)
              */
              @Override
              public void onResponse(CmsClientSitemapEntry result) {
  
                  CmsClientSitemapEntry target = getEntryById(entryId);
                  if ((target == null) && !continueIfParentNotLoaded) {
                      // this might happen after an automated deletion
                      stop(false);
                      return;
                  }
                  CmsSitemapTreeItem item = null;
                  if (target != null) {
                      target.setSubEntries(result.getSubEntries(), CmsSitemapController.this);
                      item = CmsSitemapTreeItem.getItemById(target.getId());
                      target.update(result);
                  } else {
                      target = result;
                  }
  
                  target.initializeAll(CmsSitemapController.this);
                  if (item != null) {
  
                      item.updateEntry(target);
                  }
                  m_eventBus.fireEventFromSource(new CmsSitemapLoadEvent(target, setOpen), CmsSitemapController.this);
                  stop(false);
                  if (callback != null) {
                      callback.onSuccess(result);
                  }
              }
          };
          getChildrenAction.execute();
      }
docs: Retrieves the child entries of the given node from the server.<p>
  
  @param entryId the entry id
  @param setOpen if the entry should be opened
  @param continueIfParentNotLoaded if false, and the entry identified by the id has not been loaded, stop; else store the entry in memory
  
  @param callback the callback to execute after the children have been loaded