It would depend on whether you (and the other guests) are a lacto/ovo vegetarian or a vegan. The latter would be more difficult for me, because I like to use butter, cream, cheese, and eggs...and some vegans won't even touch honey.
But I'm a really good cook, and I can make anything taste wonderful.
Appetizers would include eggplant dip (baba ganouj) and garbanzo bean dip (hummus) with whole-wheat pita.
I'd do a buckwheat pilaf with onions and portobello mushrooms.
Lentil soup--possibly curried, maybe not, depending on my mood.
I'd have mashed sweet potatoes, or perhaps a mixture of sweet potatoes and acorn squash.
If you were not a vegan, I'd make my special kugel--which my grandmother called a "nudel kuchen"--that's made from noodles, eggs, cream, white raisins, cinnamon, brown sugar, and apple sauce all baked together.
Sauted green beans with toasted slivered almonds.
Lightly-steamed kale, briefly sauted together with garlic and onions.
A Middle-Eastern mixed vegetable dish called imam bayildi (it's called that because it was "so good that it made the priest faint").
And a clafouti made with cherries for dessert (again, only for non-vegans).
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I have a friend who avoids a number of things, including dairy. gluten, high sodium, most fats, or high carb. She mentioned something once about liking gefilte fish, so I'm assuming that she's not a vegetarian, but I haven't seen her eat anything that comes from a land animal, so maybe she only eats animal protein from fish? Anyway... I fixed lunch for her in the classroom the other day from my own food stash, and I have to say that it wasn't easy finding something that she could eat. She finally settled on some canned lentil soup (this after grumbling about the sodium in it!)--which I didn't realize, until after she'd said "no dairy" and had already eaten it, that it had a little Parmesan cheese in it. See? that's the problem with eating manufactured foods: It's difficult to eliminate ingredients that one cannot eat unless one cooks things entirely from scratch (which I do at home, but not at school, due to space constraints). Cooking for vegetarians need not be a "problem" or a "big productions," but one probably should cook things from scratch.