You should not have let it get that far out of control. Now you will need to get back to a normal lawn in stages. Any metal-bladed cutter (like a lawn mower) is going to run into unseen wood and stones and cause damage. So I think your only choice at this point is to start with a gas-powered string trimmer and get the grass down to where you can see where everything is. For 1/4 acre, I do not recommend an electric or battery-powered trimmer. Electric is too slow, and battery is too heavy. Once you can see the wood and stone features, you can very carefully use a gas-powered rotary mower. For ease of maintenance, I would kill the grass within a few inches of non-lawn items such as planting beds, structures, etc. This will make it much easier to locate the items in the future.

I'd be very careful about using any kind of string trimmer close to small trees and shrubs. String trimmers, weed wackers, what-have-you, are one of the primary causes of damage and even death to young woody plants. I'm not sure I fully visualize your situation, but the description sounds like this eco-lawn is growing around and in between all these young trees. This sounds like a maintenance nightmare and would not have been my first choice of a planting design. Far better to have a designated lawn area and restrict the plantings to beds or mulched areas without the lawn encroaching anywhere near the base of these plants.

I think trimming by hand around the base of these plants is advised and keep the power equipment, whatever it is, well away.

For a quarter acre you'd do fine with an electric trimmer, and a long extension cord. They're lighter weight and quieter than gas. A quarter acre is not big at all. I have 0.2 acre and I use electric mower and trimmer with one 100ft extension cord.

the grass is too tall to use a mower on. You need to whack it down to manageable height with a string trimmer, then use a mower on it to finish it. The string does not cut as cleanly as a metal blade does but no mower will be able to cut what you've got now. Plus all the obstructions. Trim by hand around all the trees and shrubs, trust me on this one. You cannot control the trimmer well enough to always avoid disaster. No one can. Don't risk it.

I do have long handled grass shears, they allow you to use grass shears while standing but the handles are not at all ergonomic so I can only use them for a few minutes before having to put them away. Got them from the catalog Gardener's Supply. When I was on acreage I had a high wheel trimmer, which is basically a string trimmer mounted on wheels kinda like a mower. It was good for mowing down the meadow but not as maneuverable as you're going to need. Better for larger areas and ones without divots.

The highest cutting lawn mower I could find when I was in the market for one was only 3.5" high, and it was a 21" wide one. Nothing so narrow as the 8" you're looking for. That's where grass shears and string trimmers come in. Yep, sounds like you got yourself a high maintenance yard there. Sounds lovely to me, but I'd be letting the grass grow as high as it wants and just carve out trails. Once the bushes and trees are grown up the trees at any rate with shade out the grasses. You will have grass growing through and over the bushes for some time though.

Thanks everybody for excellent points, explanations, tips and advice. Won't buy a trimmer. Would never let anything harm a bush or tree! Will have to look at a variety of tools carefully before deciding and buying.

I think in our case, because there's so many thousands of slugs, we would have done just as well and saved lots of money using the erosion control mix of dwarf perennial rye and strawberry clover instead of the hundreds of dollars we spent on ecolawn fleur-de-lawn, since there are no flowers due to slug feasts. We needed the grass and self-fertilizing clover that's in the fleur-de-lawn (also available just as erosion control) as erosion control to bind the mud that was washing out of the yard daily. This thick lush green cover provides protection to the baby bushes and trees against the fierce burning sun and helps with moisture retention. Eventually the redwoods, sequoias, sweetgums, willows, maples, cottonwoods, thujas, etc -- huge trees-to-be, will shade out the grass, but by that time the tree roots will bind the earth and the trees will shade their own roots.

The fleur de lawn really doesn't get higher than 6"; it's the weed grasses that poked through it that grow really tall. And the clover mounds in coils since we have to water to wet the ground for the 300+ trees' roots.

At the moment I'm OK after using the hand shears and having my yard guy liberate the flagstones so the washer and dryer delivery men can find their way to the back patio and up the deck to haul away the old and deliver the new. Also liberated several baby bushes by hand. But that takes a whole lot of time and crawling around on hands and knees.

When I find just the right thing I'll post the solution back on this thread. Thx everybody for all this wonderful help!