I am not a doctor (or anything else "medical") so I can't offer any medical advice. All I can do is tell you what I would do if I were in your situation (and why)...
Basically, I would get a second opinion. I would contact a specialist (or two) in sleep apnea first (a different specialist) and specifically ask if over large tonsils can cause it (or make it worse, since it sounds like your little guy is really struggling, poor thing! )...
If the "superlarge" tonsils are causing sleep apnea, I would feel obliged to really consider the surgery. But if there are other, less invasive treatments (that's where seeing a specialist in sleep apnea comes in) I would be tempted to try those first.
For two reasons.
First, I know only one adult that has sleep apnea and that person had their tonsils removed as a kid.
Second, I do not have sleep apnea but do have very large tonsils. Now, I do NOT know if they are just "large" or "superlarge"... but I do remember frequent joking comments about how large my tonsils were at most check-ups growing up (I still get them on occasion when I see a doctor as an adult). I also remember getting fairly frequent strep throat as a kid and overhearing my mom talking to my doctor about having them removed. Remember, this is just a childhood memory (I was less than 8 yrs old at the time) so it might not be accurate but what I recall is the doctor wanting to take them out and my mom wanting to wait and see if they infections would go away. I can only assume that the doctor agreed to wait since I still have my tonsils today (and have not had strep throat since I was a kid).
Good luck. And with all the smart and savvy people in here, perhaps someone else will have better advice. (Hope so! )