photographing groups

[low-wattage]

Good advice above. Another thing to check is the adjustable diopter. This is a small knob near the view-finder that corrects the focus for eye-glass wearers. To do this is simple: in a controlled environment, like... the living room, put your camera on a tripod find something stark and isolated, like a wall switch, and let the camera use its AF to focus on it. Check the focus on the LCD, and then check the focus through the viewfinder. Any discrepancy and you should adjust the diopter to fix.
make sure you are on One Shot, as SwissTony pointed out, AI Servo will change your point of focus to frustration. And I always have just the center focal point activated. For the group photo, I would have bumped the ISO to 400 and shot at f/11+ to get everything in focus. Using hyper-focal focusing, I would have put the center AFspot on the baby's shoe where it meets the grass and took the photo knowing that the f/11 would make everything nice and sharp.
The baby photo is near flawless... Nice work.

[PhotoJunkieJen]

Originally Posted by kaypea

Any other suggestions? I'm to the point of wanting to buy a new camera...

Are you using the lens that came with the camera? If so, I'd suggest investing in a new lens.
I bought the Tamron in my signature and it's dramatically increased the clarity of my pictures. I haven't regretted the upgrade.