Where's the Manual?

As the kids get older I am realizing the various issues we will face...and the task of handling each one the best way possible is just a wee bit daunting. Jakeb is now 7, 7 and a half in fact. He is and always has been a serious, worrying, old soul, sort of kid. He isn't happy go lucky like his brothers, he is introspective and thoughtful. Flighty and silly. Serious and sensitive. While at first glance it would appear I am not proud of these traits my oldest possesses. However I very much am, though the problem lies not with how proud I am of him but with whether or not we meet his personality needs appropriately. As he gets older I find myself worrying more and more about him. And because he is the oldest I do not yet know if this is because he is the oldest and it is my first time dealing with these sort of issues or the worry is warranted. It is reassuring to see upon a google search of "moody 7 year olds" I find articles like this one .
I had a conversation with him today about his friends at school and he told me he doesn't play with them on the playground, when asked what he does he told me he just sits on the side and doesn't want to play because he's tired. This to me is slightly alarming, but then again is it or is it just part of being a moody 7 year old? He as a toddler was funny about things, didn't like loud noises, fast movements, certain textures of things. Etc. So he's always been a bit "different" and I have probably always worried more about him than is necessary. Or do I? Am I making things worse saying certain things to him? What are things we can do to help him deal with his differences better...are they even that different? Questions I ask myself a lot lately. Some days I am convinced he needs more than I can give him and some other support and others I think I am overreacting. I just want them to be what every parent wants for their child (or at least what they should want)....well adjusted, happy, healthy, etc etc. My family isn't full of "happy" people. We are cynicists, pessimistic claiming to be realistic, often grouchy, snappy, but oh so fun loving people. I should probably just realize that and let it go. He gets it honestly...or is something else going on? You see the dilema here....the things that start to show up as they get older is stressful. Didn't see that coming.