Having your partner at your pregnancy shoot is a great idea, apart from the obvious growing bond between a father and his child there's the visual contrast that works so well too. Including contrasting elements accentuates those features you want to draw attention to. For instance masculine and feminine, rough with the smooth, angular and curvaceous, large and small, physical strength with maternal protection even rough textured skin or tattoos highlight the softness, roundness and fragility of the bump. Having your children in the photo with you can also create a little magic, the promise of something wonderful in the making.

Playing around with images and combining them with graphic elements is one of my favourite things to do. Often the simpler the effect the better the result.

Photoshop has a number of  ways to do one thing but for me I prefer the Camera RAW processor. I simply dial down the saturation slider to 60% and bump up the contrast slider to 80%, reduce the clarity a little and you're done! The best thing about the RAW processor is you can batch process all or some of the images in one hit without having to create and  run an action. 
If you're more comfortable with Photoshop itself the 'old style' preset in the Hue / Saturation adjustment is another easy way to get a similar effect.