Conditional eager loading?

Question

I want to load an entity and it's children conditionally (I only want to eager load the children when the child.IsActive == true). How do I perform the following?

var parent = 
    from p in db.tblParents.Include("tblChildren") <-- where tblChildren.IsActive == true
    where p.PrimaryKey == 1
    select p;

NOTE: I do not want to return an anonymous type.

Thanks.