You are close. Unfortunately, this is not covered well in our client-side docs. I have asked the doc team to add more guides for client-side development.
Here is how to update data in the client-side of the grid:
var newValue; // Type: array of objects $("#C1GridView1″).c1gridview("option", "data", newValue);
The client-side widget is actually a Wijmo Grid, you can use all of the client API’s of it if you prefer: http://wijmo.com/docs/wijmo/webframe.html#Wijmo~jQuery.wijmo.wijgrid.options~data.html