chose the area for the dogs that gets some shade from the heat of the sun. Other than that not sure really.

Sadly you don't have blank a canvas. You need to create an area where your dogs can run around and mess. This needs to be an area they are totally contained in so they don't get to the rest of the garden. Hard slabbing is probably the best for this as you can keep it clean and disinfected.

The new baby is going to need safe areas to crawl and then toddle... this means no pond, no plants with spines or other prickly bits, no toxic plants, no plants that could poke said toddler in the eye... I have to say this but grass with containers might be a solution (and I don't do grass!) Of course we ignored all this and had the garden we wanted and son fell into things, over things and through things. In that sense it just depends how protective your are of your wee one. Son learned what was doable and what wasn't and at 39 is still falling over and into things!

Think about what you want from your garden. Is it a sitting area, a lot of flowers, easy maintenance, something you are going to put your heart and soul into... In that sense yes the garden is a blank canvas as you can shape it to your will but, remember the dogs and the baby :-)