Crown vetch, Oh My! :-0

Zone 6, south east PA
OK, I hear it's the plant from hell, but I need something to keep me from having to mow 2 acres of grass. (not the entire 2 acres, just cutting it down in size) I have planted lot's (close to 100) various native trees and quite a few black chokeberry bushes. Slowly picking out other natives to add. I want to "somewhat" naturalize the area. The trees are in the 3 to 5 foot range now (mostly white pine on the outskirts to hide the neighbors and closer in quite a few black gum) Just how bad is the crown vetch? In my situation, in a triangle shape, it would border a pretty thick hedgerow about 20 feet wide, an area of mature white pines (planted very close together), and what I want to keep of my lawn. I don't think it's going to do much in the dark dense pines, it might make it's way through the hedgerow into a field that is only sometimes sown every few years. Now about my yard. If it manages to keep growing and moving in, what happens if I simply keep mowing the part of the yard it creeps into? I don't need a clean cut border between the ground cover and the grass.
Keep in mind we are talking about at "least" 10,000 square feet of grass I'd like to get rid of, so planting something like Purple Leaf Euonymus would cost me thousands of $, not to mention I could NEVER keep up with the weeding until it is established. Ideally, I'd love to spread seed this fall or winter, maybe just before a heavy snow. And come spring have something that has a fighting chance with the grass and weeds. I don't care what happens to the ground cover once the trees get larger and shade out the grass.
I forgot to mention, most of it has almost full sun, some part sun. Soil is acid, the topsoil is pretty good, but has lot's of clay down 6" to 18" which causes poor drainage, and it's fairly flat too. When it's wet, IT'S WET, and in the middle of summer, it can dry out hard as a rock. By the way, most all the trees I've planted, I put them on a little mound and that seems to get them through the wet season. A couple of live christmas trees planted 8 to 10 years ago (white pine and blue spruce) are doing very well despite the conditions.
Is this just a pipe dream? Do I just have to sit back and wait 30 years for the trees to grow? I also see it attracts deer. Does this mean they will eat the crown vetch and leave my dogwoods alone, or just attract them to the dogwoods even more so?
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