We've got two giant Western red cedar trees in our backyard with nothing growing under them. I'd like to add mulch/compost and plant some native plants there. Are there any cautions for disturbing the soil under these trees? I plan to add 3-4 inches of compost and the supplier recommends 5-10 pounds of dolomite lime per cubic yard of compost. Is this OK for these cedars? I'm also interested in native plants that provide food/cover for wildlife. Any recommendations? I've got two little boys and their sandbox is under these same trees, so plants with berries that are toxic to people are not an option. Thanks!!!