Tooltip from:
['Bob', 'Jim', 'Bob Sponge'],
is coded as:
<td colspan="6" class="google-visualization-orgchart-node google-visualization-orgchart-node-medium"
title="Bob Sponge">Bob</td>
so option allowHtml:true
wouldn't help. Tooltip is just plain html title attribute. So you can use unicode for line feed:
['Bob', 'Jim', 'Bob\u000ASponge'],