Adam actually didn't have much experience preparing an event like birthday parties, but he wasn't inadequate either. He might be doing it alone in name, but actually, Amala, Callum, Kai, Isla, and even Sebastian would pass by and help him in secret.
Amala and Callum introduced him to servants who had general banquet expertise. Well, it was more like they ordered servants who had experience to help him and give him advice.
Then, Kai would come and talk randomly... until Adam realized he was telling him discreetly about Kisara's preferences. The colors and style of banquets she liked the most... the music, the food, everything else...
Isla, meanwhile, would come and help him directly. She was always that kind of person... but Sebastian would kidnap her away before she could do anything strenuous. Then, as he was leaving with her, he would dispatch more servants to help him, along with more money to spend.
