Samantha, When Justin had his surgery at 10, he had NO problems sleeping in his bed, with just a couple extra pillows. I think some of the things are a little easier for the kids, I don't recall many posts about being uncomfortable sleeping in their beds on the few different CHD boards I've been on for years.
We've never had a mechanical recliner for any of his surgeries and he was fine with our regular furniture when he was 10, and it was pretty easy for me to help him if he needed any help getting up because he was small and my back wasn't trashed.
When he had the surgeries at 17 (1) and 19 (2) we had recliners in the sectional sofa in our family room, which is downstairs and even then he had a little trouble getting out of the recliner, for the surgery where they had to move his pec muscle and he couldn't use his right arm much (the side with the button to put the chair up and down) but I just helped with that.
BUt IF you want to get a recliner, I don't know how tall Sammy is, I would just make sure the button or the handle is somewhere he can reach and push easily, since they are usually made for adults check to make sure he can reach them and that his legs actually reach to the foot part. He only used the recliner to sleep in during the day for the most part because that room has the bigger tv that has his games set up on, usually he had the recliner part down and just sat in it like a normal chair or laid on the couch with pillows.
When he was 10 he was fine during the day with our regular furniture and actually the hardest part was keeping him for over doing it, he tried to sneak sledding a week after he was home. and I caught him in the middle of the night moving a rocking chair to his room , because he wasn't tired the 2nd night home. I hear it quite often from parents of grade school age and younger kids that their hardest part once they get home, was the same, making sure the kids didn't over do or try to do things they aren't allowed to yet because they feel like they can and don't understand why they have to wait to give the bones time to heal.
For most of his surgeries, even the one where they had to move his muscle, pretty much was back to normal as far as sleeping in his bed, hanging around the house, by the 2nd week home. I remember when he needed the surgeryfor his infection 10 days after his conduit replacement, part of the reason he was so bummed was he was getting pretty much back to normal as far as sleep and being able to move with out much pain and now he had to start all over.
IF you want to get the mattress Genie, it sounds like something that would work, I know some people like a wedge pillow after surgery, but even then some people find they are harder to sleep on with out sliding down.
Since The hardest part with Justin was keeping him from doing things too soon and when he isn't recoverying from surgery or BE or whatever he was in the house for weeks for, he was an outdoor kid,playing ball, skateboarding riding his bike ect, One thing I DID try to get before surgery was different things we could do sitting down, new hobby or things his friends would probably do with him sitting when they came over. We got alot of crafts to make -some ceramics to paint, things to teach our selves how to make macreme necklaces and keyring. We'd go to the big craft store and walk around and he would get different kits he thought he might like to try. Then the usual board games.
We also had a puzzle set up on a card table to work on and when he was younger, Legos lots of lego..When we had to drive to Delaware because his PICline from BE was stuck when the home nurse tried to pull it, he asked if this was a good enough problem to get a new lego set.
