Personally, I prefer little clumps of trees to isolated specimens. I would try to work in a small orchard - say a pair of cherry trees and a pair plums close together and maybe a mulberry farther away, with a couple of smaller, more colourful flowering trees nearby. Then a few staggered along the fence-line.
It's entirely a matter of taste, and dependent on how you plan to use the spaces underneath. Just keep in mind what's self-pollinating and what isn't.
