D.W.
S.,
I am an audiologist who worked consistently with kiddos in the clinic before I went back to school. If your son is scheduled for pressure equalization tubes, that means he has fluid behind his ear drum that will not drain or absorb on its own. Chronic fluid can often lead to speech, language, and hearing deficits. It can also lead to secondary issues, like the balance problems you described in your son. Others have reported it as clumsiness with or without delayed gross motor development (crawling, walking, etc.).
The doctor will suction the fluid before placing the tubes. You should notice a difference relatively soon in his responses to your voice. However, I do not recall reading anywhere about how quickly his motor skills will get back on track.
Good luck and I hope you all do well. Take care!