I’d ask him what he wants, and do that, unless he already has a past that tells you he will manufacture a big traumatic drama where none exists. If he has already made some big deal about seeing someone all banged up, tell him you will not find that helpful. Do not act as if seeing you with bloody bandages that you asked for and expected in order to make you better is something that ought to traumatize him. It might upset him, but there is no reason it ought to be upsetting because you will only* look *bad.
a) this could be extremely boring, because while the doctor has an estimate about how long it will take, the surgery will go until the surgeon is satisfied it has been done correctly. He is not going to speed it up because an 8 year old is bored. Your son needs to take that into account, because your husband is not going to be able to take him home if he changes his mind. Teach him that delays in surgery are an inconvenience, but not something that should automatically worry him–because that is what they would be.
b) you’re going to be looking kind of rough and would appreciate not having him act like you look like an evil witch or had you nose sawed off or something. A little “you look like you got into an argument with a truck and lost” humor will be OK, but otherwise you’ll need him to pretend you look better than you do. In other words, your looks will be more of an affront to your vanity than to your safety, and you need to treat it like that if you want your son to do so.
In other words, do not make this sound worse than it is. It is going to look worse than it is and seem worse than it is, but this is not a big deal. If he’s ready to sign on for that, then let him be there.
Your husband is not going to be allowed to watch, let alone your son. He ought to plan on being with you while you’re being prepared, wishing you well, and then leaving the hospital with your son for somewhere more pleasant. He can come back in four or five hours. Make it clear to both your husband and son that you will manage fine if they are not on the hospital campus when you wake up. It will be enough to have visitors shortly after you wake up, which you will appreciate, if they won’t be upset seeing you looking awful. If seeing you look awful is going to make them look like they’re seeing death, though, thanks but no thanks. (If you are not worried about him or yourself, it will make it easier for him not to worry.)