Planning a 2 Course Meal for 3 People Plus a Lacto-Vegetarian
Okay. I think the terminology for that type of person is more typically "lacto-vegetarian" or just "vegetarian" since "vegetarian" implies no meat but the possibility of other animal products such as dairy.
I think there are three approaches you can take:
1) Make a vegetarian entree that appeals to everyone. Manicotti stuffed with ricotta cheese, spinach, and mushrooms might be a good example. Check the back of the Barilla manicotti box for a good recipe (seriously!). Other possibilities might include lasagna, bean chili, lentil soup, etc.
2) Create some sort of do-it-yourself dinner option. That might include make-your-own pizzas or make-your-own tacos. You would provide the crusts or tortillas and your guests would top or fill as they see fit.
3) Serve a meat-based entree with a variety of vegetarian sides. Serve everything family style rather than plating it for your guests. That way, each guest chooses what he or she likes.
#1 would be a single dish for all, but brings up the question of whether one person's preferences should dictate the choice for everyone. It might depend on whether your other guests expect meat at every dinner.
#2 might involve a bit more shopping and set-up but can be fun and would allow each guest to customize to his or her needs.
#3 is viable as long as the sides are filling enough to be a meal in themselves.
What about a vegetarian casserole type dish with cheeses, as suggested above, and then, if someone insists on meat, you can have a grilled chicken breast as well. Kind of like when people these days add grilled chicken to a Caesar salad. Only serve the chicken on its own platter, family style. If there are leftover chicken breasts, well, heck... anyone can use a spare grilled chicken breast!
Not quite a "2 course" meal suggestion, but what about a number of tapas or small plates dishes. Empanadas, spanish omelette, meatballs, apple and walnut salad, piperada, ajillo mushrooms, rice stuffed peppers, marinated olives, mussel/clam dish, etc. Flan for dessert, or bunelos w/ vanilla ice cream, or arroz con leche.
Greek/Mediterranean dishes might also lend themselves well. You could do hummus, baba ghanoush, toasted pitas, falafel, souvlaki, taramosolata, tzatziki, moussaka, spanakopita, orzo salad, etc. Baklava for dessert or just a bottle of ouzo.
If you are set on a 2 course meal, you could do salad w/ a few different quiche options.
Don't worry about the lack of meat. If your meal is good, the other folks will enjoy it.
I can't think of a better excuse to do an over-the-top macaroni and cheese. Something with a a terribly rich cheese and interesting shaped pasta, possibly garnished with truffle oil or a dollop of a fresh, spicy pesto. Pair that with a simple spinach and fruit salad (apples pears, raspberries, quince paste or dried cherries) and a good bottle of white wine such as Elk Cove Pinot Gris.
Now I'm hungry.