In order to reduce the choices in the genus Fraxinus, I think you should collect a branch and bring it somewhere to get closeups.
Snapping the compound leaf off the stem will reveal the leaf scar - or collect enough branch to show some of previous years' leaf scars - and this will give more information to separate species. Also, showing buds will help. Many of the Ash members have different color and pubescence on the buds. Ash will also vary in how glaucous the undersides of the leaflets are.
Fall foliage color is another way, but we'll have to wait a while to see that.