Hi my dd had this operation when she 4yo for similar reasons (chronic glue ear and sleep apnea) she also had some grommets fitted at the same time.
I had stocked up on softer crisps like quavers and skips also marshmallows, the consultant said to me it really didn't matter what they ate as long as they ate something! I was also advised to take a favourite drinks bottle in with us to encourage her to drink afterwards.
Post op wasn't very nice as dd was obviously in pain and did have quite a lot of blood in her mouth however she was given some morphine which helped and she did perk up a bit by the same evening. However in total i would say it took a good couple of weeks for her to fully recover. She found the experience quite overwhelming and was very quiet and not herself for a little while.
I would advise on having a quiet week or two post op (was told to keep her off school for at least two weeks anyway due to risk of infection) with lots of time for cuddles and watching tv. Also stock right up on call and ibrufen, dd needed this 2 hourly for quite a few days.
Hope I haven't scared you even more op
but I wish I had been a bit better prepared tbh! It was worth it as breathing and ears were much better post op.
Oh and another thing I hadn't been prepared for was that for a while after the op when dd had a drink a small amount would dribble out of her nose!! No idea how common this is but it did freak me out a little bit first time it happened.
I had also bought dd a gift (talking Annabel doll) for being brave which went down well and was a good distraction.