Thanks a lot for your advices! Yes, my son is suffering from motion sickness, that was the main reason I would like to drive on my own- so no hassle with the driver to stop several times etc.
Never heard about these wristbands- but we will definitely try these out. Booking a car (family car) from Germany with all insurances would cost me $460 for four days.
I am not worried about driving 'left hand side' but the mentioned road conditions seem to be a challenge.