No more stress! From what you described, grass doesn't have a prayer under your Magnolias. Select a mulch or gravel that will look nice and of course it won't have to be mowed! Pea gravel would be best I think since it will prevent muddy feet and paws from making their way inside (Stress...). To add a rustic look, make a border of rough cedar logs around the edge of the gravel. If you prefer a tidy look, use bricks, rock or pavers.