RE: the pain - when dd had her tonsils out her consultant said there was absolutely no reason for her to have immediate pain post-op, and that once we were home, if we kept to a strict schedule of pain meds then we could stop the pain before it started IYSWIM.
She had the anaesthetic, and also during the op they gave her a suppository with super duper pain relief. We had private health insurance. The op was at 7pm. She was back in our room by 8.30pm I think. Doped up. Had supper (tuna sandwich and some ice cream).
Then a nurse came about 4 hours later, as the suppository wore off, and gave medicine. Apart from one other time in middle of night at home, that was the only time she was properly sore. We were given a prescription for codeine.
She healed really well. No infection, no refusal of food or drink.
I had a humidifier in her room overnight to keep the air moist and to try and stop the dry throat ache.
She was playing in the garden the day after the op, once we were home. Went back to school just under the fortnight after the op (was summer term, so she didn't want to miss the meet the teacher afternoon where they get to meet the next teacher).
She was 7 though - so older than your ds. I think it was a great thing for her to have the tonsils out. While she didnt have recurrent infections, she had huge enlarged tonsils all the time, which meant she mouth-breathed. Had stinky breath and sleep apnoea. Snored like a train. Was rather underweight. All that's stopped now - sleeps really well now, eats well, no stinky breath and most importantly, no apnoea. A side effect has been that she hasn't had a single day off sick from school in the last 2 years! Has been really well. :)