Interplanting with new fruit tree seedlings, what can I plant that won't outcompete???

I am composing a planting of new fruit trees in zone 5b in a yard. (I already know to kill all competition like grasses and the like) I am looking to plant from seed fruit trees (so they will be first year trees) in close density (7-10 feet apart as we are trying to keep the small). 6-8 feet in front of them (toward the sun) I will be planting a row of grapes. In between the row of grapes and the fruit trees I will be burying weeping tile for subterranean irrigation. With regard to the fruit trees, I would like to plant some Nitrogen fixers. I was looking at Siberian Pea shrub or Goumi. Seaberry has thorns and has a tendency to spread too fast. I was looking to plant a number of comfrey and alliums (Egyptian walking onion, or chives) as well as a few pollinators with medicinal uses. Maybe some perennial ground covers like mints or strawberry? I know that once the sunlight diminishes, the spreading stops.
I just want to know if the Nitro fixers will cause problems in the development of the trees and out compete them? I am working in a very tight urban space so I have to keep them pretty close (from the property/fence line to the tree will be 3-4' and the Grapes will be 6' in front of the trees((again facing the sun)). The soil PH is high currently, but that can be corrected.
Can you give me any advice, or experience you may have with this type of planting??
Are there better companion plants to be used? Are there any plants that will really help the development of the trees?
The Fruit trees that will be going in will be Apple, Cherry, and Peach.
Thank you for all you help!

Hi,
Out of the things you were looking at I would suggest goumi because it stays smaller and both Siberian P and sea berry have thorns. I believe nitrogen fixers tend to grow fairly quickly compared to the other trees, except maybe the peaches, though I believe you can trim them back fairly heavily to encourage them to put nitrogen into the soil.

Just plant the nitrogen fixers and then prune them regularly. This will be the best for the soil and for your production trees in the long run.

I have a Siberian  pea shrub, the thorns are minimal
Consider prairie mimosa, they don't grow very high and have delicate compound leaves.

I like to plant blueberries or blackberries in front of the trees after thay have been growing for a year or two.

Ken Crum wrote:Hi,
Out of the things you were looking at I would suggest goumi because it stays smaller and both Siberian P and sea berry have thorns. I believe nitrogen fixers tend to grow fairly quickly compared to the other trees, except maybe the peaches, though I believe you can trim them back fairly heavily to encourage them to put nitrogen into the soil.

That is my understanding as well. Many nitrogen fixing trees can be cut back severely and they grow right back. Part of the support they provide for fruit trees is not just fixing nitrogen, but also to add food and mulch for the fruit tree from their trimmings.