I am afraid it would not be possible to use RadChart/RadGridView for Silverlight within Telerik reporting at the moment. While the Silverlight Report Viewer is a Silverlight application, it only displays the report as generated on the server. Within the report you can take advantage of the Telerik Reporting Items described in details here
the Telerik team
Do you want to have your say when we set our development plans?
Do you want to know when a feature you care about is added or when a bug fixed?
Telerik Public Issue Tracking
system and vote to affect the priority of the items