Since the objects of different classes will have different sizes, you would end up running into the slicing problem if you store them as values.
One reasonable solution is to store container safe smart pointers. I normally use boost::shared_ptr which is safe to store in a container. Note that std::auto_ptr is not.
vector<shared_ptr<Parent>> vec; vec.push_back(shared_ptr<Parent>(new Child()));
shared_ptr uses reference counting so it will not delete the underlying instance until all references are removed.