I'll go to the field with anywhere from 1 to 6...all depends on what's in the trailer, what I need room for, what needs work, etc etc.
As a general rule, I like to have one "really nice" airplane (big gasser, for example) and one "toss in the air and bang around" airplane (say, a park flyer or stick or something like that). I'll also load up the giant tele if the kids are going, or if I have a student to work with.
Other airplanes (maybe a smaller gasser, warbird, something) might go along as well if it's going to be a long day.