Wherever you possibly can, simply leave the leaves to begin to replicate the natural process in our woodlands. This is particularly important under trees. Lawns are a challenge for large trees, given their compacted soil, limited space for roots and competition with grass for access to water and nutrients.
Fallen leaves provide a natural mulch to the ground and the plants, helping retain soil moisture and insulating the soil from temperature extremes. As the leaves decompose, they provide nutrients to the soil, and a majority of butterfly/moth species actually use the leaf layer to complete their life cycle. Of course, we understand other areas will remain tidy and leaf-free for turf grass.