rabbit54, try to ask in advance about the hospital procedure on the day itself.
The hardest thing for parents is to hand your most precious things in the world to the anesthetist. It is possibly the first time you have had to absolutely trust another person with your child's life.
Suprisingly, once you have given your baby over, a calm will settle because there is no longer anything you can do.
For my dd, who went for open heart surgery at 4 months, I got dh to carry her to the operating theatre. I followed behind. All the anesthetists and other staff were already scrubbed up and turned round when we entered the room. Dh gave her to one of them, and we were cheerily ushered out of theatre with reassurances (I never registered a thing, of course). The last I saw was dd being lowered onto the narrow operating table and a mask being fixed over her head.
She had a catheter put into her hand before the op - that was pretty traumatic for me as well.
Dd had to starve for the op. I got my MIL to comfort her because she was still bf-ing and I was concerned she would smell the milk on me and go hysterical if I refused. As it turned out, dd fell asleep in grandma's arms. Probably tired out from crying due to the catheter insertion.
Ask whether there is a queue of operations on the day itself and which number your ds is. Very frequently, if an earlier operation takes longer, your ds' operation will be delayed and he may have to starve for longer. Be prepared for this.
Definitely see if you can room in, if your ds is required to stay overnight.
All the best to your ds.