My 6 year old grandson had his tonsils and adenoids taken out last year when he was 5.
He also had gromits put in because he had become quite deaf.
He had problems from about the age of 3 just like your son.
He had to stay away from school for a few weeks after the op so he didnt any germs that were going around. After that he was fine.
In fact he became a different child. His school work had been poor, mainly because he couldnt hear properly.
After the op he started to enjoy school, and he is now on the same level as the rest of the class.
When asleep he used to snore, and woke up several times during the night. He now sleeps through till morning.
He doesnt keep getting infections all the time.
His mum wishes he had had the operation done earlier, because it has made such a difference to his life.
They also now get a complete nights sleep.
I know your son seems very young to have an operation, but it is probably better to have it done now, before he starts nursery school. He can only better.
Good luck