My partner's best friend (let's call him Tom) loves to throw parties once in a while. Some of the people he invites he's got to know them from online video games (that's how he met my partner), some of them are friends from work, some are his partner's friends, and lastly, some of them he met through other types of activities, namely sports, concerts, school, etc. This means that most of the time, these parties gather people with very different backgrounds, jobs, hobbies and topics of interest.
What he does to make sure everyone's having a good time and has the chance to get to know the others and chat with them is similar to what you offer: he's a big fan of board games and usually plans to play at least one during these gatherings.
Plan group activities
Board games, video games, dancing contests like Just Dance, blind tests, these are all activities you can plan to make sure everyone's going to interact with each other and gets a chance to enjoy themselves in the meantime. The trick with these is that they can get a little difficult, especially if you don't like them in the first place. For instance, I hate board games. I just can't stand it, it bores me to the next level. However, Tom knows how to make it interesting, by planning his game leader act ahead. He comes up with a story and he makes us laugh and interested in the game. I'd recommend you try to have several activities planned ahead though, so that you don't end up helpless if your friends are not interested in the game you picked up. You're going to be the concrete binding your guests together on that night, as they'll be there to celebrate your special day with you. Try to trigger conversations that they can continue to get to know each other when you go to see another guest.
Some other important points if you want to bring the best out this party:
Think of everyone's needs. Some people don't drink and may have a hard time enjoying themselves if they don't have soft drinks by hand. Some others may need to go home early, don't blame them for doing so, just thank them for coming. It's likely not to be personal, they may just be tired.
Enjoy yourself. This is your special day. People come here to celebrate you, bonus if they can meet new people. The tricky part is that you're likely to have to be available the whole night, as you'll be the one bringing all your guests together. But don't forget to enjoy yourself in the process.