You should be able to use multiple selectors separated by coma. Please see the following example: http://dojo.telerik.com/UnOW
In fact any valid CSS selector can be used and your selector looks valid. I assume that the problem is related to the mark-up of your page. Where are the .sortable elements located? Are they inside the #MyGrid element?
Check out the Telerik Platform - the only platform that combines a rich set of UI tools with powerful cloud services to develop web, hybrid and native mobile apps.