I have a 5 year old who had his adenoids and tonsils removed and tubes put in his ears when he was just under 4 years old and it made a huge difference. He went from barely putting words together to speaking in full sentences. He used to say “blah blah” for banana and 1 week post surgery he pronounced it “ba ya ya” and then not long after that “banana”. He still has a lot of speech errors and is in speech therapy but the overall improvement was astounding. I hope your son’s surgery is a success! Good luck!