Sounds fun! Here’s my favorite relatively chill multiplayer games:

• ToeJam and Earl - the ultimate chill vibes game, punctuated with moments of panic, of course.
• Gunstar Heroes - marvel at the peak of 16 bit graphics, blow up badguy robots, find cool gun combinations, repeat
• Cyborg Justice - incredibly steep learning curve, but a chill repetitive gameplay loop with lots of interesting mechanics to discover
• Battletoads vs Double Dragon - Probably the best brawler, with lots of interesting twists in gameplay mechanics. But starting with 3 lives is unfair - use the Konami code for a chance to see the whole game.