Nice pictures. It does look like you underexposed them somewhat which resulted in the darker orange skin tones. In bright sunny conditions it is more difficult to get the proper exposure though. Overall a nice job though. Some things to consider:
- When you shoot, how do you judge brightness? If you are looking at the picture on the back of the camera then that will fool you. You should always have the histogram viewable. You want to push it to the right at far as possible without blowing the highlights. For example, the pretty little girls dress I assume is white, yet in the photo it is more gray indicating underexposure.
- In bright sunny conditions, place the sun at your subjects back and use flash. The camera will underexpose if you don't use flash because it will meter (on evaluative) for the bright conditions. The flash will brighten your subjects preventing underexposure and give catch lights in the eyes.
- Do you shoot raw? If not, I highly recommend it. It allows one to fix exposure mistakes more easily than jpg because it retains more data. It has saved me a bunch of times.