I can tell you're going to spray these weeds some time in the near future. If so, spraying them first is fine. The weeds you have don't lend themselves to being plucked by a Weed Hound, but if you have a problem with tap rooted weeds, you might consider getting one of those tools.

You can avoid getting weeds next year by seeding heavily NOW and having a nice dense turf for spring. A tall dense turf will keep most weeds from sprouting. Just because you have crabgrass this year does not mean you have to have it at all next year. Also setting your mower up high and watering only weekly might completely prevent weeds.

Before I quit using chemicals I used to prefer spot spraying with the Weed-B-Gone products versus the RoundUp family of products.

One thing to point out is that if you spray the weeds with a broadleaf weedkiller (such as Weed B Gone), you'll have to wait for some time before planting (I think it's a couple of weeks, but it's on the label). If you use Roundup, it'll kill everything, including your existing grass, but you'll be able to plant in a few days (again, check the label to find out how long, especially since there are new versions of roundup that are long lasting).

Do you know when your average first frost is? You may be pushing things seeding this late. If I remember correctly, there are pockets of SE PA that have pretty late first frosts, but conditions can vary widely over a fairly small area. You don't want to seed with less than 6 weeks before you expect a frost. You may be too late to seed already, or you may be ok as long as you don't treat the weeds.

i think i won't treat the weeds,as it seems most is crabgrass, which i believe will die off soon anyway, and then i'll address the crabgrass in the spring...

can i spread the seed, then aerate after the next rain? as the soil is clay, and very hard right now due to lack of rainfall..i have about 1 1/2 acres of lawn, so to irrigate it won't be practical

If you keep it moist. Just moist, not wet. No puddles. Keep moving that hose with nozzle right along, briskly.

I don't think it's practical to try to water 1.5 acres with a hose or hose-end sprinkler.

If you're not going to get enough rain soon enough for germination before winter hits, you may want to consider dormant seeding. To dormant seed, you wait until the soil has cooled too much for the seed to germinate and spread the seed then. The snow will help take it into the ground as it melts, and in the spring, when the ground is moist naturally, the seed will start germinating as soon as it's warm enough. You'll lose some to birds and insects, and you may lose some to premature germination if it warms up enough to germinate with a cold snap following too soon, but if you're trying to seed without any additional water, you'll probably get the best results with a dormant seeding.