Наследование, массив объектов дочернего класса внутри родительского

#include <iostream>
#include <memory>
#include <vector>
#include <string>
 
class Base {
public:
  virtual ~Base() = default;
  
  virtual void sayMyName() const { std::cout << "Base\n"; }
  
  template<class T, class ...Args>
  Base& addChildren(Args&&... args) {
    m_children.emplace_back(std::make_unique<T>(std::forward<Args>(args)...));
    return *this;
  }
 
  //...
  
  void callSayMyName() const {
    sayMyName();
    for (auto const& child : m_children)
      child->callSayMyName();
  }
private:
  //...
  std::vector<std::unique_ptr<Base>> m_children;
};
 
class DerivedOne : public Base
{
  int m_id;
public:
  DerivedOne(int id) : m_id(id) {};
  void sayMyName() const override { std::cout << "DerivedOne " << m_id << '\n'; }
};
 
class DerivedTwo : public Base
{
  std::string m_id;
public:
  DerivedTwo(std::string id) : m_id(std::move(id)) {};
  void sayMyName() const override { std::cout << "DerivedTwo " << m_id << '\n'; }
};
 
int main()
{
  Base().addChildren<DerivedOne>(666)
    .addChildren<DerivedTwo>("Azaza")
    .addChildren<DerivedOne>(777)
    .addChildren<DerivedTwo>("qwerty")
    .callSayMyName();
}