Quoted:
i would guess if they were devout enough for you to worry, they wouldnt come to your house and eat. If they know who you are and are still willing to come you should be allright.
I don't think it works like that. It's not like they have to keep Kosher.
You could always ask your co-worker if there's anything in particular you need to do.
As long as you're getting the meat/poultry/whatever from the halal market, you should be GTG, right?
And just in-case, you might want to check the ingredients of anything else you serve (e.g., biscuits, gravy, etc) since sometimes beef broth or lard is an overlooked ingredient. Just imagine you're cooking for a vegetarian and you should be cool.
Reminds me of a place I used to work where the team consisted of a Muslim, a Jew, a Catholic and a Christian Vegetarian. Deciding on a restaurant we could all agree on for lunch was an "adventure" almost everyday.