*Here*  September would be considered the best time to seed a lawn.  In your area,  you might do fine in August.  I would agree that you want to wait until the hot days of summer are over.  

I like using a light coat of straw to cover the soil, and help keep the soil from drying out.  I believe there are mulchs you can buy to help the same.  I think the key is going to be keeping the soil moist until that grass is up and growing. 

Depending on what your workload is like, if I was in your shoes, I might consider breaking those 2 acres up into smaller segments,  seeding 1 segment each week, so I could keep up with it, and make sure it gets started.  I would consider this especially if I could water a portion of it, but not water the whole thing at once.