And yes. Those are CCS Sakura and Syaoran.
Their wish to Yuuko, in order to help their son, had them pay with their lives literally. Their time was rewinded and they were trapped within the tube. So, therefore, the Sakura and Syaoran at the very beginning of the manga are those of CCS.

Yuuko explained how their relatives left them in her care. Touya and Yukito.