Yeah, it's just like when you're ordering a bunch of pizzas for a group. Always get a couple with just cheese, or all veggies. This will help all the employees feel included in the party, no matter what their dietary preferences may be.
You also want to have something sweet, and a fruit tray with some kind of creamy dip is always a good option. Just have several kinds of fruit on the tray.
If you know you've got chocolate lovers at your party, you could offer little chocolate cookies with a cream cheese dip or something similar at the end of the meal.