I understand you not wanting to feel like some sort of freeloader, Phobius.
And I totally respect that,

but consider...
Kuv has just put the town through a real mess with his "Kirby" fiasco, and would like very much to do something nice, for the sake of his OWN guilt.
Now it is seems to me that I never paid you for your courier services last season.
So...why don't you come by the shop in
this "PM to join" thread I'm doing with Redire. It's right on the 1st, so it's a likely day for you to come seeking your pay.
This would allow you to meet Redire, if you haven't already. And you could casually mention your birthday. Kuv would quickly see this as the means to make amends both to you and the city in general.
IC, Kuv could invite Aislyn, Nanami, Redire, Yisanareysin and Darkalin Pinewood. From there, they could invite anyone they know. Naia, Vard, Zeke. Not everyone signs the register after all.
Plus which, Kuv could be handing out flyers about the party to customers at the shop, so there could be general knowledge in town, which could account for increased NPC attendance. The promise of food, drink and entertainment would bring them in.