How to throw my first BBQ?

That actually sounds like a really fun party! If it is going to go long into the night, you could probably show a movie using a projector on the garage door for fun! Have lawn chairs because people like to sit. Your food options are very good and well varied for everyone. If you wanted anymore food ideas you should have a BUNCH of fruit...definitely watermelon because it is such a summer food. I would also add something as simple as cookies to the dessert because not everyone likes cheesecake or pie. It would be cool to set out picnic blankets or something for everyone to eat on.