Your son will be able to take notes however he is most comfortable, paper and pencil are fine, especially if that method aids him in doing his academic best (and that’s the point, right?). No one will criticize him. But, don’t be surprised if, after a trimester or two, he picks up a few other tools. Kids seem to organically absorb any technology that makes things easier (or more fun) for them, and Choate does offer assistance and training on electronics and application use, but it seems the kids show/teach other the tricks of the trade as they go along (e.g., “Hey that’s cool! How do you do that?”). If he’s stressing about this, please tell him not to. He will acquire whatever level of tech savviness serves him best just by immersion in the community. In the meantime, paper and pencil will work just fine.
BTW: When our son was in your son’s shoes, he was worried (really worried) about the sports requirement as he had never participated in one, and that’s not something easily fixed. Or so he thought. Once on campus, though, those fears melted away as he joined a team that welcomed him, taught him, and helped him become a varsity athlete. I’ve posted many times that crew was the best thing he got out of Choate. OTOH, he was one of the tech kids with multiple monitors and a full-blown desktop graphics, video/camera, and printer setup in his room. He was happy to show his new dormmates how to do things, and he let all of Mem House send homework and other documents to his printer. If your son had been been in Mem House at the time, our son would have happily helped him with anything he needed. I’m sure your son will find plenty of ChoatieKids on campus when he arrives.
I know our experience is no longer current, but I have no doubt it is still relevant.