Use Spot metering mode and/or get and use a hand held incident/reflected/flash light meter, dial in some exposure compensation to adjust for all the white in the scene.
Lighting, accurate exposure, and sharpness are keys to professional quality portraits.
I do not agree that the exposure of the images is acceptable as work product for a photography business.
Consumer grade cameras and consumer grade kit lenses don't deliver professional grade sharpness.
The least expensive way to improve image quality is to upgrade the photographer's artistic, technical knowledge and skill.
A knowledgeable and skilled photographer can make high quality images using consumer grade gear, and judicious post processing.
Using Photoshop's Camera Raw I measured the RGB luminosity value of the highlights on the child's cheeks, forehead, upper lip and chin.
I got values for the red channel of 180 - 200. That indicates under exposure. Facial highlights should be in the 235 - 240 range in the red channel when the exposure is correct.
I can not show you that, or the photo corrected for the under exposure because you have chosen -
My Photos Are NOT OK to Edit.
In other words, the photos are under exposed, and under exposed by a full stop.
What is a "Stop" of Exposure in Photography? | Photography Mad
A likely way that happened with your photos is because of the white background and the light metering mode your camera was set to. You likely used what Sony calls Multi-Segment metering mode.
A DSLR's built-in reflected light meter is calibrated based on the assumption that the vast majority of scenes that will be photographed with the camera will have an average reflectance equivalent to 12% to 18% gray.
When there is a lot of white in a scene (white background, snow, a white wedding dress) the built-in light meter gets fooled and reduces the exposure to make it equivalent to 12% to 18% gray.
Understanding Camera Metering and Exposure
If you look closely, your background is indeed a light shade of gray and not white. The gray backgound is most noticeable in the last photo where the baby has the beads in hand.
So knowledgeable and skilled photographers know that when there is a lot of white in a scene they have to take the built-in reflected light meter's exposure indication with a grain of salt and do a couple of things:
1. Add Exposure Compensation (EC) to account for the fact all the white in the scene is fooling the light meter. (page 79 of your a290 user's manual)
2. Use a light meter mode that doesn't meter the entire scene. (page 81 of your a290 user's manual)
https://docs.sony.com/release/DSLRA290.pdf
Essentially, you will need to understand a vast majority of the information in this group of tutorials -
Digital Photography Tutorials
Plus you will want to be skilled at using image editing software like CS 6.
The goal though is to get it as close to right in the camera and then use Photoshop to finish the image rather than to fix technical errors.