SQL Reporting :: Mapping ObjectDataSource With Complex Data To ReportViewer And GridView?

I have a data object where one of the properties is a collection of another data object. I never really figured out how to map this to a GridView, but I came up with a workaround. Now I am stuck and cannot figure out any way to do this in a ReportViewer.

Here is how I solved the GridView issue:

Say we have these objects:

public class BoysWithToys : List<BoyWithToy>
{
}
public class BoyWithToy
{
string FirstName { get; set; }
string LastName { get; set; }
int BoyNumber { get; set; }
List<Toy> FavoriteToys { get; set; }
}
public class Toy
{
int BoyNumber { get; set; }
string Toy { get; set; }
}

What I wanted to do was to map BoysWithToys to the GridView and present one GridView row per BoyWithToy record. Where there was more than one FavoriteToys record I wanted to list them in a bulleted list in the FavoriteToys column. I accomplished this by calling RowDataBound() for the GridView, casting the e.Row.DataItem to BoyWithToy, then looping through all of the FavoriteToys and adding each Toy to a bulleted list, then setting the column's text to that list.

I have no idea how to accomplish anything similar in ReportViewer. If I simply drag the BoysWithToys DataSource to the designer and run it, the FavoriteToys column shows '#Error'.