When my dd went to the tea party, we had no problem parking there at all. If the guard stops you at the gate, just tell him where your going and have your confirmation number handy.
My dd didn't dress up for it, a few little girls did. She had a great time. While she was there we stayed around the GF, had coffee and sat outside. She loved it so much, as we loved the resort and the following summer we stayed there.