When planting shade garden plants... I'd worry less about those plants having issues with the trees...
they evolved to fill that niche!
I do think that you are trying to plant more there than the site can support...
If you want to go perennials, fine...
if you want to go shrubs, fine...
but... it just looks too small there for both.
Planting under trees can be difficult... finding any soil among the roots.
even just planting perennials... you are going to have to back away from the trunk...
although... there are shallow rooted perennials that would happily fill that area in right up to the trunk... like strawberry begonias.... and some of the native running ferns...
