Geoff Lawton suggested in his recent PDC that coppicing is best done at the end of the growing season (fall) when precipitation exceeds evaporation, when leaves are at their most over-mature but the stalks of the plants still have enough sap to heal from the wound before winter dormancy, but also that some of the sap has already returned to the roots for winter.
In the spring, the stored sap will rise and become fresh shoots for future coppicing. Coppicing creates a
compost corridor as the roots related to the coppiced branches will, over time, rot in place, and for your needs will release the nitrogen that is related to the roots which correspond to the particular coppiced piece.
If you snip up the coppiced branches of a nitrogen fixer into smaller bits, they will provide more readily available nitrogen as chop and drop mulch. It seems that you have mature enough stock to begin just trimming some smaller branches and feeding them to your fruit trees on the surface, while potentially directly benefiting the fruit trees with root based nitrogen transfer, if they soil communities have merged.
Regardless, if your nitrogen fixers are close enough to your fruit tress the soil communities will eventually merge, nitrogen will be exchanged, and coppicing is not as necessary... though you may desire to do so anyway to increase nitrogen for your fruit trees, to mulch them, to provide other trace nutrients/minerals, to give them more light.