Two plants I can suggest that I have chosen for my garden, are virtually unkillable, will grow in almost ANY soil or weather conditions & require little maintenance are: butterfly/african iris & Celtic Cascade tree. Both can be left to go a little wild for a natural look, or be cared for, to fit perfectly in a more formal garden. In regards to the iris, I removed my entire garden of mature, property damaging trees when I moved into my new house, but didn't want to wait years for a new mature garden, so I searched online for ppl selling/giving fully grown specimens away before they did renovations or re landscaped! The plants were a cinch to dig up, replant in my heavy clay soil & are thriving! I even cut some of them in half before planting and it didn't phase them!

What a beautiful big space! I believe you posted this in the wrong forum. 'Design Dilemma' would have been a better location for it, hence the no replies. What does the end result look like?

Consulting a Landscape Architect or designer is going to be time and money well spent. Taking in the location and aspect of the yard. What you and your family want and how you want to use the space for, will help in creating the design. A good landscape designer can be found through you local landscape industry association and will be able to provide a cost estimate to construct the project. Then if you are going to get contractors to quote the work you will be getting quotes based upon the same brief and not random impressions based upon verbal interpretations which can only confuse your decisions. If your going to do this project your self then ask your designer how they would program the works and how to stage construction. Best of luck. Hope to see the finished job !!

Can you post a sketch? I'm scrolling back and forth trying to visualise it all and understand dimensions and orientation and usage. If the fence colour suits the house and creates a good background for the plants I wouldn't worry about whether it will date. The same concern could apply to the house, but if it all comes together in a way that is classically timeless rather than overly trendy and you're happy with it, then it's working. Alternatively formal or informal hedging can obscure the fence and avoid the question of what colour the fence should be. I agree that with a toddler and dogs you want to keep as much of that lawn as you can. Work out how much garden bed is needed around the edge so that you are not constantly pruning the plants back to fit, but so it still leaves as much lawn as you want. What's missing in my view is edging, most garden styles look better with edging between the plants and the grass. Another thing that gives gardens a more finished look is underplanting. Research plants to ensure you don't plant anything that is toxic or allergenic. Remember humans and dogs can differ in that regard. Start an Ideabook for your garden. If you have images of what you are trying to achieve, and you can share that with us, you can make progress with specific how to's and choosing specific plants.