As far as grandstand seating, you cannot view dressage OR stadium competition without purchasing some kind of stadium seating, which is additional to your admission to Rolex at the “gate.” If you’ve never gone to Rolex before, that might be a surprise because in the old days, you could stand and watch both events from the fences or try to get a bleacher seat by getting there early.
Also, you can no longer camp in the Ky Horse Park campgrounds on a “whim” as all the campsites are booked completely on the day AFTER the current event is over! They take reservations 365 days in advance, and so that’s what everyone does. I think you can still get a primitive site ( no water/electric/etc) by getting there early with your tent or camper.
A little preparation for either blazing sun or pouring rains will make you more comfortable should either, or both, happen! One year we even had tornadoes!