Dolph was there in very non-seasonal clothes (blacks and dark reds), did his rounds (and by rounds I mean he said hello to Narcissa, kissed Chloris on the cheek, and then found somewhere to sit down and read near the festivities). He was reminded why Narcissa was his favourite socialite when he discovered the books she'd set out for him and Corbina, and read those instead of the two he'd hidden away in his robes.
Sometime in the middle of the ball, he might have gotten up to ask a few people to dance.