Son's surgery scheduled in three weeks...please advise

Thanks for reading my post. My son is 12 years old and was diagnosed last year with a cerebral AVM. It is 3 cm, sits atop the brain and has shown no signs of bleeding. His surgery is Thursday, May 26th.

I am writing to ask those of you that have gone through this experience already, do you have any advice you'd be willing to share? The hospital where his surgery will be performed does allow one person to stay overnight in the ICU. Is there anything special that you would recommend I do/bring to the hospital? Of course, I will check the hospital policy to see what is or is not allowed, but is there something you wish you would have thought to bring or do?

Those of you that have had the surgery, can you please describe your experience? My son and I both would like as much information as possible as far as what to expect? Were you in a lot of pain? Is there anything that helped to alleviate your fears/anxieties leading up to your surgery? Is there anything that helped to keep you more comfortable after your surgery? I am doing everything in my power to plan and prepare for this. It is the biggest thing our family has ever gone through and I want to make my son and my two daughters as happy and comfortable as possible.

Thank you all in advance for any advice that you would share.