PEPPER was obviously there, sporting her engagement necklace that Tony made her (as she already has a ring) situated right above the node. She was a little emotional at the surprise of it all, made sure to find out who all helped so she could thank them personally, was social with every person who attended, and danced all the dances with anyone up for dancing. She loves dancing. Dance with her.
JAMES was in the thick of all the planning and set up, even when he was being incorrigible with Thalia over donuts, and he's just THRILLED TO PIECES that this is all happening. He ditched the jacket, tie, and slicked ginger hair as soon as things started getting thrown around outside, but he was in and out of the main party frequently, and while he didn't dance a TON, there were definitely choice dances.