It's too late for you to seed. That should have been done late August/early September.

Weed and feed is also not the best way to fertilize and control weeds. Much better to use seperate products, especially with the herbicide so you can target the weeds you have.

Not to mention that weed and feed's optimal application time (April) doesn't coincide with the correct time to feed for the first time in spring (late May).

It's wiser to spot-apply herbicide as needed on established lawns, and feed separately.

And +1 ForsheeMS; it's way too late to seed in Connecticut. The correct time is when summertime temperatures just start to drop in the evening and you say to yourself, "It's not really the middle of summer any more." Usually that's mid-August for me, probably early to mid August for you.

I think the idea the OP is getting at is will the WnF be a problem for new grass six months later. The answer to that is no. However, as has been mentioned, seeding this late in the fall is not a good practice and neither is using weed n feed. You will likely be disappointed with both.

Weed n feed has several problems with it. It's hard to use properly and the results are not usually what you were expecting. Spot spraying individual weeds is a much better way to do that.

If you have thin spots or if you are starting new, you're going to want to seed in the spring. Spring is not a good time to seed new grass, but if you have to you have to. One problem with that is you usually get a dose of crabgrass at the time time. If you do, you won't have to live with crabgrass permanently. It can be eradicated, but you will not have a gorgeous lawn for summer 2015. However, with some planning for next August, you can have a beautiful lawn for 2016.