My son has them every 8 weeks, they’re fairly straight forward under GA,
Is your DS going to a children’s hospital for it? If so, they’re brilliant (he’s been scanned at 2 different children’s hospitals) very understanding and child centred, gentle wake up too.
You won’t be allowed to stay with him when he’s under GA, too risky, but, of your hospital has a different approach and you can, make sure you leave bank cards, mobile, pager (yes, I’m that old) and anything that can be interfered with by the magnetic waves. (I’m not allowed to wear my insulin pump during my scans)
With regards to comfort,
Favourite teddy/blankie/you/toy
Something to drink after, as he will be starved and not able to drink before the scan.
Something light and bland to eat after, (my DS likes cheddars, and they seem to settle his stomach)
Remember to ask for vomit bowls for the drive home after, it may be worth asking the anaesthetist to give your DS an antiemetic after to prevent him being sick.
They should tell you if he’s had pain relief, and recommend what you should do/who to notify if there are any problems post GA.
Hope things go well for your DS, my own will be on his 110th GA at the end of next month, kids are tougher than they seem.