You can either concatenate the HTML as strings:
$element.html($delBtn.html() + $updateBtn.html())
Note: This will copy the elements and not move them.
Or add the elements into a single jQuery object/collection to append:
$element.empty().append($delBtn.add($updateBtn));
or http://jsfiddle.net/TrueBlueAussie/0bp2h0Lu/
$element.empty().html($delBtn.add($updateBtn));
Note: These will move the elements (which is what you specified).
You are better off using the other methods like empty() to clear it and append() to add children as that will be faster than re-parsing the HTML and re-creating elements.