The crab grass, fescue, creeping Charlie, dandelions, and other "weeds" are all organic matter that have been growing in that soil taking nutrients out of that soil, so if you remove them you would be throwing away valuable nutrients.
Till them in, put them back where they came from, recycle the nutrients they pulled from that soil.

Take a good, in depth, look at the soil to see what needs to be done. A soil test for soil pH and major nutrients is a first step and these simple soil tests may also be of some help.

1) Soil test for organic
material. From that soil sample put enough of the rest to make a 4 inch level in a clear 1-quart jar, with a tight fitting
lid. Fill that jar with water and replace the lid, tightly. Shake the jar
vigorously and then let it stand for 24 hours. Your soil will settle out
according to soil particle size and weight. For example, a good loam will have
about 1-3/4 inch (about 45%) of sand on the bottom. about 1 inch (about 25%) of
silt next, about 1 inch (25%) of clay above that, and about 1/4 inch (about 5%)
of organic matter on the top.

2) Drainage. Dig a hole 1-foot square and 1 foot deep and fill that
with water. After that water drains away refill the hole with more water and
time how long it takes that to drain away. Anything less than 2 hours and your
soil drains’ too quickly and needs more organic matter to slow that drainage
down. Anything over 6 hours and the soil drains too slowly and needs lots of
organic matter to speed it up.

3) Tilth. Take a handful
of your slightly damp soil and squeeze it tightly. When the pressure is
released the soil should hold together in that clump, but when poked with a
finger that clump should fall apart.

4) Smell. What does your
soil smell like? A pleasant, rich earthy odor? Putrid, offensive, repugnant
odor? The more organic matter in your soil the more active the soil bacteria
will be and the nicer your soil will smell, to a point. Too much organic matter
can be bad as well.

5) Life. How many
earthworms per shovel full were there? 5 or more indicates a pretty healthy soil. Fewer than 5,
according to the Natural Resources Conservation Service, indicates a soil that
is not healthy.

Once you know more about the soil then you can make a plant to address any short comings.

Hey Kimmq, I've seen you post this test before; when I do the jar test, should I remove all the roots and vegetation from the soil sample? Also, when you say till in the turf, do you mean incorporate it with a spade or fork, or literally rototill?

Use a spade, a fork, or a rototiller, whatever you have available to turn those plants in. I have used all known methods with good results. The spade, the fork, etc. are a bit more work than a rototiller but the results are similar.

When doing the jar test, that can be done anytime, remove the large pieces of organic matter and any stones from the soil sample, Your state ag school, the Cooperative Extension Service, may have soil sampling instructions on line, or this from UMASS (University of Massachusetts) may be of some help.

Skip -

Save yourself a lot of work. Mow the area as closely as possible, leaving the mowed material on the ground, and spread a thick layer of wood chips (6-8 inches) over it. Any old shredded branches or leafy branches will do, freshly shredded is preferred.

The roots left behind, and the top mowed material will also improve the tilth.

It will block light and prevent weed seeds from germinating. And it will rather quickly improve the texture.It encourages all kinds of beneficial micro-organisms. By spring it will be about half as high and ready to plant.

In the spring, make small holes for your perennials and plant them into the mulched area.

Take care of any weeds that make it through the mulch, but there shouldn't be many.

If, skip, you have several years to wait then what lazy has suggested will work. However, to be able to plant in the spring you will need to till in organic matter now so it can be mostly ready by spring. It takes quite some time for wood chips to be digested and incorporated into the soil and that will not happen over the winter. Possibly, after tilling in enough organic material, you feel the need to spread a thick layer of wood chips that could be done, now, but only after the soil has been amended well.