Just an FYI but the Bloomerang lilac and both the dogwoods (large and small) are just shrubs, not trees. I'd also wonder how much shade the 3 existing evergreens to the south of this planting area might cast, especially with regards to the fruit trees - they benefit from a full sun location.

If you want level play areas you have to build a retaining wall and fill in behind it. Your yard does not slope much and the retaining wall would probably not be more than 12" high. Fill dirt can take several years to settle, so plan on having concrete piers in the ground for the support poles to sit on. The retaining wall could be fairly wide as you have to make the level area not just large enough for the swing support poles, but also allow for the arc of the swing outside the support posts. A swing/slide could go in a shadier area than the pool. You should put the toddler pool on the patio, and take your child to a public pool as he gets older. All the issues of creating a level area and allowing fill dirt to settle are much more important for an above ground pool, because a U.S. gallon of water weighs 8.3lbs. A 12' round pool that is 4' deep contains 2,975 gallons and weighs about 24,692 lbs. If this small pool collapses the resultant flash flood would damage your yard and the drainage easement downstream.

Thanks for the comments. It’s a small yard so I was hoping to get more useable space but I don’t want to spend too much and it sounds like this would be expensive,

How about a dry stream bed starting at the vanishing point of your stepping stones and meandering along that same arc? Then develop a pathway adjacent to it, with native shrubs and grasses along the outer edge?