The "caca" will do very little to change the pH of the soil. The pH will be pretty much like the rest of your yard. You could use the material as mulch elsewhere in your yard if it would be too thick where it is. Sorry, I can't help with plants in your zone.

tj

Well thanks for that info anyway!
Now I can just go to a reputable nursery and get deep shade plants! Thanks! NT

Look for plants that are tolerant of dry shade. The area under or adjacent to the canopy of large conifers is typically rather dry - the canopy prevents rain from penetrating to the ground easily and the extensive root system of the trees sucks up whatever soil moisture is available. Ditto with nutrients. You need to start small and provide additional water and fertilizer to help plants get established in this area.