If you have the space (e.g. your conference room), a short 10-15 minute networking exercise that could form a small part of your evening is a geographic mapping thing…
You stand at the middle of the conference room (chairs need to be out of the way!) and say something along the lines of "OK we’re going to try to make a map of where we’re all from… where I’m standing is where the venue is.
If you’re from North of here, go and stand up there, in front of me. if you’re from south of here, go stand behind me, from East of here, go stand to my right, and from the west, go over to my left".
Then let chaos ensue for a bit as people try to find where they live in relation to other attendees, until you have lots of small groups chatting away with people from - hopefully - somewhere near where they live.
Keep an eye out for anybody standing on their own because they’re from Greenland or somewhere, and shepherd them to the nearest group.
You can use it as an ice-breaker that isn’t excruciating for participants, gets them into small groups, and potentially enables them to go away with useful contacts that are local to them…
You could follow it up with a speed dating thing where you get everyone into two parallel lines facing each other and give them 30 seconds each to give the answers to 3 questions (you choose what they are) to the person facing them. After they’ve both spoken, everyone shuffles up and one of the people at the ends swaps sides, so the whole thing essentially rotates.
This way people get introduced to everyone else without any awkward silences or smalltalk, or people boring each other. Could take a while with 100 people though.
Once you’ve done all that you could do anything - a ceilidh is often good to get people loosened up and meeting lots of other people by dancing with them. Can be a bit intense for folks who hate dancing or are introverts etc. though.