tough question not knowing the layout, 800' is not much but you do want to get as many people in there as possible. The ADA will only require you to have on handicap bathroom, your building inspector will make sure you comply and an isle for a wheelchair. The health dept will also have a set seating capacity for you based on square footage and # of bathrooms. I have to tell you that no county is the same, I have one store that did not need ADA. and each of my stores has one bathroom and 50+ seats.
I guessing you can fit aprox 12 small 2 top tables 24 chairs, but again hard to figure without a layout. Order some tables and add more as you need them.