Hello Devin!
First you have to ask yourself how much light reaches the forest floor. You'll need to measure it in full sun, and in the cloud cover, to guesstimate light levels of the relevant seasons, like spring, summer and fall. Full sun is typically 8-10 thousand ft candles while just the open sky on a shaded side of something is about 4 thousand ft candles. Do you have a light meter? Can you properly prune those
trees to get more light? Can you thin those trees to get more light? The amount of light will depend upon the species you can grow. When dealing with plants that are shade tolerant, they tend to grow much slower, and not deal well with much grazing. If you're asking this question. I'm guessing its not much light, or
the answer would already be growing, from seeds blowing in the wind. To establish shade tolerant perennial plants could take years. Then you would most likely only get one grazing per year, without harming your work. Those are some things you need to think about. When you come up with answers as to the level of light you're dealing with, and your USDA hardiness zone. The numerous answers and easiest solution will be easy to give.
Hope that helps!