How adventurous are your friends?
If they're up for anything and you feel like going all out, you could try something like this:
If you'd like something simpler, I can recommend this:
Savory Mushroom Stew
I like it over mashed potatoes, but since it's spring and it would be a dinner party, I'd probably serve it over noodles, with some bread to sponge up the sauce and a salad.
There's always a baked pasta dish. Almost everyone likes them.
This is a good one and feeds a crowd:
Baked Penne with Roasted Vegetables
Or if you want to have something low key and fun, what about a chili night? There are literally a million vegetarian chili recipes on the web. Black bean is my personal favorite. You could put out a bunch of toppings: green onions, salsa, guacamole, sour cream (dairy or nondairy...Tofutti vegan sour cream is remarkably close to the real thing, imo), and a big bowl of tortilla chips for people to dip into. Maybe with a dark Mexican beer?
Or mushroom fajitas are always a big hit with my friends and family. I think for that I'd go buffet for a party, with the same toppings you'd use for chili and sides of rice and beans.
What kind of an evening were you thinking of? I love meal planning/dinner party planning, if that's not obvious!