I would serve fish, lean meat and vegetables for grilling - don't know how fancy you want to make things, but cutting both into pieces and putting them on skewers would be a good idea. Maybe marinate some of them?
Then I would have a salad bar - lots of different things to put in salads, and a dressing or two or three so that everyone can make their own salad in varying degrees of healthyness.
And I'd offer some bread, too, maybe home-made garlic bread so you can make it with more garlic and less butter. Obviously that depends if bread is a trigger food for you, I know it is for many people. On the other hand most people I know will always have bread with something grilled. Depends on you and your friends, really.
For drinks you could offer some beer and/or wine for the two who are drinking, but also get something a bit more fancy than water for the two of you who are not drinking - maybe home-made sugar-free iced tea?