Firstly, I’m not a garden designer, but I just wanted to talk about putting ideas down either on paper or digitally. I’m using my sketch app on my phone to work something out. It’s a bit scruffy but gives you an idea. I’ve used a short oblong because it’s approximately the shape of our garden. I’ve drawn in some of the trees using the elipse tool. Then marked in possible paths using a ruler tool for straight lines. Then filled in with a spray tool. I’ve added a blue patch to indicate a pool and sprayed in colour where I want flowers. As there are a lot of trees I’ve shifted the flowers over away from shade although you can get woodland flowers to cover the ground below the trees.
Basically it’s worth doing a drawing if you can to get an idea of what you want. Also work out the compass points. Then you will know where plants will do their best.