Ok I went out today taking some pics. I think my camera has focus issues. Not one picture came out really clear or sharp. I am going to upload some of the raw images to dropbox and link to them below.
Dropbox - IMG_1820.CR2
Dropbox - IMG_1821.CR2
Dropbox - IMG_1841.CR2
Dropbox - IMG_1844.CR2
Dropbox - IMG_1833.CR2
Dropbox - IMG_1840.CR2
Dropbox - IMG_1825.CR2
Dropbox - IMG_1832.CR2
Since you posted these as RAW images, I downloaded them and opened them in Canon Digital Photo Professional 4
IMG_1820 - you selected center focus point and camera nailed focus. The image needs a bit of exposure adjustment, but focus is fine. You used manual exposure and f/5.6
IMG_1821 - you selected the center focus point and camera nailed focus again... but the subject is in motion and I do see some left-right motion blur (duck was moving his head). You also used manual exposure and f/5.6 again.
IMG 1841 - you selected the center focus point and... I'm noticing a pattern here... again, you used f/5.6.
Ok, time to talk about f-stops and why you would choose one over another.
f-stops control the aperture size of the lens which has a strong influence on "depth of field" (the range of distances at which subjects will seem to be in acceptable focus... not that's "acceptable" not "perfect") When you are shooting a single subject at a given distance and don't care if objects at other distances (such as backgrounds) are in focus, you can select a low focal ratio. In fact doing so can render a strong background blur which is sometimes highly desirable (although these strong levels of blur usually comes when you also used moderately long-ish focal lengths and the focal ratios are particularly low... f/2.8, f/2, f/1.4, etc. you wont see strong blur with a shorter focal length and f/5.6 ... you'll get just enough blur to realize it isn't "sharp" but not enough to be "artsy".
But then you shoot the pond with a near-shore, a tree stump on the near shore, some rocks on the far shore... and you focused on the middle of the pond... where there isn't much interest.
If you want the "whole" scene to be in fairly good focus... use a higher focal ratio... f/11 or f/16 for example. f/22 will give you even more depth of field but if you REALLY pixel-peep the image you may also start to notice that while everything is "pretty good" that the best parts aren't as sharp as they might be down at say... f/8. This is due to something called "diffraction limits" and has to do with the wave nature of light (it's a physics problem... not a lens problem or camera problem.) You can do some pretty cool things at f/22.... shoot a night-scene with street lights and notice that at f/22 the lights turn into "stars" with diffraction spikes coming off every point of light (a nice "artsy" effect.)
So far I'm looking to see if you'll change the f-stop to anything other than f/5.6.
IMG_1844 - another f/5.6 shot that would have been better at a higher f-stop. I see you set the center focus point. It looks like there *might* be a tiny bit of camera movement in this shot. It also looks like the nearer part of the scene might be slightly better focused than your chosen focus point. Might you have moved the camera just a touch after focus? In "One-Shot AF" mode the camera will only focus until it achieves focus and if the camera moves at all after that, it will not update the focus again. When using that mode it's important to not move the camera after it locks focus.
IMG_1833 - another f/5.6 shot that would have been better at at higher f-stop. Like IMG_1844 I see you used the center AF point and it's not as sharp as the closer parts of the image.
Your lens MIGHT be front-focusing... or your sensor MIGHT need a shim adjustment (sensor plane might not be orthogonal to the optical axis of the lens) or your lens MIGHT have a decentered element. It's hard to tell.
IMG_1840 - hard to tell
IMG_1825 - this one looks pretty good. I see you put the focus point on moving water ... which might make the focus system struggle a bit.
IMG_1832 - this one looks pretty good.
Now back to the original image...
Those two kids look microscopic in this big image with all the rest of that clutter. As Robert Capa is quoted as saying "If your pictures aren't good enough, you aren't close enough."
Back to my commentary on what might be wrong (besides shooting everything at f/5.6 regardless of what depth of field might work better for your subject). I'm somewhat skeptical of a decentered lens element or non-orthogonal camera sensor (e.g. needing to be shimmed) because if that were the case, is think i should see the issue in _every_ image... not just some images.
When you want to test a camera or a lens, eliminate any possibility of human error or problems with the subject. Go shoot something you can control.
Find a FLAT brick wall. Put the camera on a tripod. Make sure the camera lens is perfectly orthogonal to that wall (wall is perfectly parallel to the camera sensor) -- nothing is on an angle. You need something "flat" so that you can be sure everything is in the plane of focus (with the caveat that technically the plane of focus is fractionally curved so don't expect corners to be quite as sharp as the center.)
Since your photos are typical outdoor landscape photos ... your foreground is nearer than the background and we can't quite be sure why part of an image has better focus than another part.
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