How many different things should I serve?

It sounds great. SOunds like you have many varieties. When it comes to serving foods, you need atleast 1 fruit and 1 vegetable or salad tray, etc...and 2-3 different types of meat, wether its beef, pork, chicken, or fish. And the filler ideas are good too. The chips and dip are a good idea, along with the nuts. Sounds like you have it covered