You could make a pretty spring stew with white beans and asparagus. (Use olive oil in place of butter)
http://outoftheordinaryfood.com/2012/03/16/spring-stew-with-white-beans-and-asparagus/

You can make the whole thing ahead and warm it up on the day.

Or chickpea pot pie, if you make the crust with olive oil (or buy vegan crust or puff pastry, or just top it with mashed potatoes!)
http://outoftheordinaryfood.com/2012/11/20/chickpea-pot-pie-sweet-potato-hashbrowns/

Here's a creamy vegan coleslaw with almond dressing...
http://outoftheordinaryfood.com/2012/06/27/creamy-vegan-cole-slaw/

Moroccan spiced chickpea stew with red peppers and artichoke hearts, which you could serve with couscous..
http://outoftheordinaryfood.com/2012/08/26/moroccan-spiced-chickpea-tomato-and-pepper-stew-couscous-semolina-bread/

I make a "lasagna" with chard or kale leaves instead of pasta. This one has walnut ricotta. Use vegan mozzarella or leave it out altogether, and omit the eggs and water from the ricotta.
http://outoftheordinaryfood.com/2013/01/28/chard-lasagna-with-fennel-roasted-reds-olives-and-walnut-ricotta/

I have made this spring stuffing recipe ahead a couple times. I just get everything ready and in the casserole dish the night before, and then pour on the broth and bake in the morning.

http://ohsheglows.com/2012/04/02/lightened-up-spring-stuffing/

Orzo salad: Orzo, peas, minced shallot, olive oil, lemon juice, lemon zest and red pepper flakes.

Vegan stuffed mushrooms - easy to prep and then cook later:
http://www.organicauthority.com/appetizers/vegan-sausage-stuffed-mushrooms-recipe.html

Sorry, I just thought of another - these little butternut squash dumplings have an olive oil crust, and roasted butternut squash and pecans inside. (Use soy cheese, obviously!)
http://outoftheordinaryfood.com/2012/01/21/butternut-squash-pecan-dumplings/

And you serve them with this pecan-whole grain tarator sauce, which is delicious, creamy, and completely vegan. This sauce would be nice with any kind of roasted veg, actually! You could serve it with "steaks" made from roasted cauliflower, butternut squash, or portobellas, and it would make them fancy and delicious!
http://outoftheordinaryfood.com/2012/01/20/pecan-whole-grain-tarator-sauce/

I love making eggplant caponata on the weekend and then you can use it as a sauce on anything-- rice, pasta, portobellas, cauliflower steaks or florets, or non-vegan options-- chicken, fish, etc. And of course, it's great as a dip with pita, on a sandwich, and so many other options.

This is what I'm making for Easter -- it's more of a main dish, but it can easily be made ahead and is SO delicious!

http://ohsheglows.com/2012/10/05/glazed-lentil-walnut-apple-loaf-revisited/

You can assemble these roasted peppers filled with tempeh stuffing the evening before and then bake them the day of. After you've made the stuffing and filled the peppers, arrange them on a baking dish, cover, and store them in the fridge. That way all the prep work is done and the only thing you have to do on the day of serving is to pop them in the oven. And then eat them, of course. :) Bonus? If you use tri-colored peppers they come out so bright and cheerful. Perfect for a spring entree.

Roasted Peppers with Sicilian Tempeh Stuffing
http://www.braisenwoman.com/2012/10/roasted-peppers-with-sicilian-tempeh.html

Suzanne Goin's White Bean gratin is time consuming but totally worth it. You can make it a day or two before and bake it the day of. With a green salad, it's a complete meal.

The link to the recipe: http://www.freshtart.net/White-Bean-Gratin-16386833

This vegan kale caesar is great! I like to make the dressing ahead of time and toss it with the salad right before serving: http://rosemarried.com/2013/01/06/vegan-kale-caesar-salad/

Vegan dirty rice. http://7th-taste.com/2011/11/13/frugal-foodies-night-vegetarian-dirty-rice-with-barbera-dasti/

These recipes sound amazing. I cant wait to try the White Bean Gratin.

We are vegan and I (think) we'll be making
1.) a spinach salad with red onions, walnuts, sunflower seeds, mushrooms, beets, oranges and a honey-mustard dressing which you would dress right before serving.
2.) baby carrots with maple and lightly with either ginger or curry.
3.) green bean and onion mix too.
or a quinoa greek salad... I havent decided.
4.)I think for a main, we'll do a lemon piccata with portobella mushroom caps with either a red potato or basmati rice side.

This is a yummy spring recipe:
Cook pasta to package directions - any kind but I like penne
While pasta is cooking, juice 4 lemons in a bowl
Add pine nuts and 1 cup chopped parsley in bowl
Add pinch of salt and pepper
Drain pasta and add to lemon juice mix and toss.
Let sit at room temp until ready to eat.
Your guests could add Parmesan or nutritional yeast (vegan, cheesy flavor) at table side.

Dessert: Coconut or Almond Milk vanilla bean ice-cream topped with a shot of Kahlua. Your grocery store should carry dairy alternative ice"creams"

Thank you for accommodating your vegan guests! We appreciate it!