Too much grass seed is not a good thing. As the seeds germinate they will end up fighting for space, light, and nutrients. You are better off waiting until the first batch has taken root and then doing it (or waiting until the spring).

Just buy more grass seed and a hand spreader (Amazon has one that I use) and do it on top of what's there. If they already aerated, no need to do that twice. Water it consistently.

The only downside to reseeding twice is the money you spend. You certainly won't do any harm to what's there.

So my lawn company just told me, after I wanted to fire them, that i should have arated and seeded my lawn. I just had that done from my landscaper (i'm not sure how good of a job). Should I do it with my lawn service as well in a few weeks? Is there any danger from doing it twice? I just don't know how good of a job my landscaper did. thanks