Thanks for advises! I think the most effective way to start overcoming fear of Valter is to start operate with him. I will try to invite my son in teleoperation session with joystick remotely from another room or from outside of apartment. Also I will try to invite some children, friends of Igor, which I know for sure from previous, enjoys how Valter looks and behaves to demonstrate that there is no danger from Valter side. In other words - continue Valter’s socialization process 
Thanks for your words of approval!