Is this just a board for people to tell their personal stories? Trespassing is never okay. Trespassing begs for trouble. Put up a No Trespassing sign to let them know, and then take legal action if/when you can. What BS to say plant prickly hedges and mazes. That's costly and leaves you maintaining it. What BS to say it only bothers you if you let it bother you. If someone is opening your fence gate just to cut through your yard and jump the back fence, that's blatant disrespect and plain wrong. If you don't have a fence, then mark your boundaries. I am assuming most trespassing stories here are fence hoppers/yard runners. I don't know what to do about acres and acres of "tresspassable" land. But nobody should be short cutting via established private property. Those kids accidentally break plants, planters, fence slats, gate locks, etc., and perhaps they'll fall and get injured, or see something through your window which might, perhaps, lend thought to a later "return". Nobody should have to tolerate trespassing, and especially not because some other person decides it's no big deal for "them" so "okay" to trespass. Some people won't find your kids as amazing as you do, so don't force them into showing it. Don't be that moron parent.

Here are a few photos. In all three, one can clearly see the shape of the edge of the lawn, but not what creates it. I like this look, and it can be created with a subtly colored/camouflaged stone or brick edge. (If the photos embedded in this thread are too small, follow the link below each to get to the photo set for each and you can click on the photo there to see a larger version.) The all look to be relatively newly created and so plants will get larger and fill in over time. You don't want to overplant and create a dense thicket. Having sight lines into the woods or a path to a shady seating area under the trees would be nice. In this first one, I am not particularly fond of the abrupt in/out edges between the grass and wood, but it does have a variety of plantings of different heights, some of which are just outside the tree line and some within the trees. There are small flowering trees, some medium flowering shrubs, and low-growing groundcovers between. http://www.houzz.com/projects/29439/grand-rapids-residence In this second one, I would add plantings outside of the tree line, a combination of trees, shrubs and evergreen groundcover as I think that the transition from grass to established woods is too abrupt, but again here there is a clean edge, a combination of flowering shrubs and smaller trees set into the understory. This one, like the first photo) is taken in very early spring before the leaves fully fill out, so it is likely to look fuller/denser when there are more mature leaves. http://www.houzz.com/projects/337408/woodland-gardens In this third photo, ignore the patio in foreground and look across at the far side of the lawn. Another clear edge and a combination of ornamental small trees and shrubs that transition to denser native woods beyond. The birches were probably already there, and they cleared around them and then added the shrubs. I prefer groundcovers to the bare mulch look - more attractive and easier maintenance. http://www.houzz.com/projects/1749687/perched-lake-and-mountain-views

You have options! As long as you mix some of the tones from your house into the exterior living space, you can add in grays. The best bet would be to go with warm grays to help blend the warm and cool spectrums. Consider adding gray to your home's exterior on the structure itself to create a fully cohesive palette. Best of luck with your project!

One aspect that makes your yard appear "unfinished" in my opinion is how visible the neighboring houses are. Even if you don't want 100% privacy, which many people don't, it would look better if the long stretches of empty fence were interrupted by some plantings -- large trees or shrubs mainly ... possibly some large masses of perennials. How exactly, depends on your goals and expectations. I would keep plants in a deep band near the perimeter ... all within a border bed, separate from the lawn so as to eliminate some mowing and give the appearance of separation from the world beyond. I would also have the bed be filled with a single, durable, uniform groundcover so that I wouldn't need to be mulching every year or looking at brown. But you might be satisfied with just mulch. Cheap? Start with small plants. Fertilize and water them and they will grow.