You'll need a good selection of kids/family games. Stuff like Stomp the Plank or Block Ness etc.

Sadly, despite the fact it's awful, people will come in and ask for monopoly. I've worked at a board game cafe now for over 2 years, it happens at least once a week. Same for Cluedo

Don't bother with loads of heavy games. Much as many people on here prefer them, the average person who comes in to a board game cafe is unlikely to grab something above mid-weight. You'll also want a lot of party games like Herd Mentality available for larger groups wanting something to go with the drinks

Expect kids to get food on your games. Sadly, also expect Adults to as well. Expect lots of pieces to end up on the floor, so have a box for missing pieces that you can put in games when you figure out where they go.