Look, I have no major objection to Karwa Chauth (bigger battles to fight etc) but this Bollywood idea that only North Indian festivals are mainstream is nonsense. With that in mind, please tell me something cool & slightly obscure your family celebrates.
For eg: near my grandparents' house in Hyderabad was a Tamil family that set out their dolls on a table every year? Like all sorts of clay dolls and teeny tiny doll's house furniture type things & that day they welcomed all us surrounding kids inside with open arms.
No idea what that was about, since I haven't seen it since, but I always wanted to touch it but there was this aura of museum-ness around the display that meant I couldn't.