Trivia is a great activity. I like it when you have a ton of mini-rounds of 2-3 questions under some category- you can leave plenty of time in-between questions so people can come up with an answer and then still have time to chat and get to know each other. For your goal specifically, I would just try to avoid topics that are kinda gendered and stick to stuff that isn't. Biology, history, music, pop culture, literature are all great topics. Throw in some oddball questions, and keep a really broad scope so you can learn which of your new teammates is really into Bill Murray and knows what language he learned, what instrument he learned to play and what art form he practiced in Groundhog Day, or what is the common name for Amorphophallus titanum, the Sumatran flower that is the largest flower in the world and arguably the smelliest.

Trivia is cool because it gets your brain going in a lot of different directions in a short period of time, it can spur some ideas for the rest of your hacking. It is also competitive while still being fun, and unlike a tournament, you get to play the whole time whether you're in first place or last. If you have a Final Jeopardy style final question, you can totally come up from behind and win if you're the only team that knows it, so it's never pointless to keep going. Giving out prizes for various special rounds is great for that too, like a round where you have to identify songs based on a 15 second clip, or brands or celebrities based on a picture. Think about how you want teams to form, and what size works best for your group.

Rock on with being mindful about the culture you're creating. Lots of devs love competition and violence like that, and lots of devs don't.