Ceremony seating issues!! Help!!

Okay ladies, so my wedding is in a small town in Northwest Indiana called Rensselaer. My wedding ceremony will take place by a lake with a HUGE open field and my reception will be at the fairgrounds inside of one of their buildings. I am struggling with figuring out what to do with seating. I want to do the chairs, but they are expensive ($3/chair) and I have 150 guests at my wedding (we both have huge families!) I was possibly thinking like picnic and putting down blankets, but I don't know how people would feel about that, plus the elderly people may not get up or down. Any other ideas?