First, if I were in your shoes, I would want to make sure there is not a case of Tinnitus/ Vertigo as this is more serious and involves other treatment.
Tinnitus has a 'ringing' in the ears sometimes due to blockage or other ear conditions (such as allergies/ viruses).
Vertigo is more of the 'dizziness' and will set of bouts of nausea/ vomiting, involuntary eye movements and there is difficulty with motion (such as with your little boy now seeing the scenery.)
Ginger does help, as does nutmeg, peppermint and spearmint (essential oils) but I am not sure if this is what you are referring to? If so, you want to be sure you are purchasing 'safe' oils as many are tainted in the stores. (I get mine from France & Hawaii.)
You can try homeopathics, just research a bit further with a reliable book. Mine recommends 'Cocculus' as this is a the most common remedy and preventative. More does go into selecting your remedy, so if you want to contact me privately, I am VERY happy to help you! ;)
(You can find at a good health food store. I have the best luck with them for my own things and my son's colds.)
I would not recommend herbals as the age is too young for my own comfort level.
Acupressure points can help, but not sure in this case as it would need to be done before and after for sure. You could look into 'seabands' (for motion sickness) but something feels wrong about it as they stay on and it may be too much for a small body.
I do hope it is just a simple motion sickness? If that is it, maybe try giving a focal point? Not sure if that would work as well as using the homeopathic, but it could. My son always brings a toy with him and that is his 'focal'. I never did get motion sickness until later when I was a teenager. I cannot read in the car now without becoming ill! (the words move too much for me.)
Good luck!