Is this your 3 year old who you wrote about with a heartbeat question?
If it is, I'd like to mention two things. His heart and his speech.
It seems to me that you haven't had a lot of time to digest this. Have you taken him for testing to a pediatric cardiologist? Has he worn a Holter for 24 hours? (Probably hard for a 3 year old.) Has he had an EKG and an ultrasound of his heart?
I would no more walk into surgery without definitive answers than the man in the moon. You should make sure you understand this regardless of what the ENT says.
Now, about your son's speech. You should know more about your child's palate structure before you agree to the surgery. Does he have a short soft palate? How is his speech? Does he sound nasal AT ALL when he talks? The reason this is important is because a short palate needs a ROOF so that it doesn't have to work so hard while speaking. The adenoids are a roof. A child with this can end up having permanent hypernasality if the adenoids are removed.
An xray is not enough to determine this. I promise you. Your child needs a nasal endoscopy. A light and camera will show the adenoids and the entire structure. That structure needs to be taken into account. The adenoids CAN be shaved and minimized without taking out so much that the roof of the palate is compromised.
How do I know all this stuff? Because I went through it with my own son. His tonsils were removed, and thank God, the ENT actually understood what he was looking at because he only shaved and minimized my son's adenoids rather than take them down to the nubs. He saw my son's structure and understood that he needed that roof. BUT, fast forward 2 years when we lived in another state, and my son had a lot of sinus infections. A new ENT told me that he needed his adenoids removed, without as much as an xray. He wouldn't answer my questions, he wouldn't do any diagnostic tests. I found another doctor who was willing to do a nasal endoscopy to see what was going on, and that ENT was wrong. My son's adenoids were not the problem. A surgery would have done nothing but cause pain and more speech issues than he already had. You can bet I didn't go back to that guy.
Please step back and deal with the heart issue first. Then ask for a nasal endoscopy to talk about your son's structure and make sure that his speech won't be adversely affected.
I promise you that it's worth it.