Shrubs and 1 tree

[Beothany]

I'm planning on the space I want to use for my meditation. I've decided on 1 tree surrounded by shrubs.
the question is what would be the best to use?
I was thinking about using a Birch tree, or and Oak tree (I live in Iowa It needs to be strong) But I have NO CLUE about hedges or shrubs or whatever I'm supposed to call them.

I also need to know how far back to place my shrubs (?) that way they don't interfere with the roots of the tree. i want this to be around for a long time. long enough for my children to see it.

please help if you can