Wei Wuxian is there! With his Lan Zhan because Aawwww romantic but also they just love music?? He will enjoy this a lot because one of his favorite things is just sitting nearby and peacefully listening to Lan Zhan play music or playing with him. SO there will probably be gross amounts of PDA* (by that I mean maybe they will hold hands. if Wangji lets him.)
Toph is there to support her teacher and also she likes music, can feel the vibrations and doesn't have to WATCH anything like so much media, so she'll actually be pretty pleasant listening to it. She'll just lay on their group blanket and prop her head up on her hands and listen like she's got headphones on.
Evie is there! Probably ish around Jacob and Serefin but not too close in case they want to be gross, she also wants to support Vanya and likes music!
And Atreus is Dorian's personal space heater and it's Romantic.