Depends on the definition of "no meat"... some will eat fish, or eggs, either of which gives you a protein base.
Another option is to serve the kind of meal that you put together at your plate. Chef salad, for example - various veggies and toppings, including things like sunflower seeds. Or tacos - refried beans are also protein, and the other toppings are according to taste, including optional meat.
Some people will serve hamburgers... and grill oversized portabella mushrooms to serve as an alternative. Never had it, so don't know how good they are, but some people like them.
If you can solve the main dish, sides are easy: anything veggie! from veggies and dip, to squash, to steamed veggies to... the world is wide open. (For me, solving the protein thing would be the hardest. )
Dairy-free isn't hard. If you have something in mind that relies on dairy, let me know and I'll see if I know of alternatives. One that I have no alternatives for is cheesecake... But, just as an example, if you wanted to serve fruit salad and ice cream for desert, you can get (or make) a lemon sorbet - not sherbet, which still has dairy, but a true sorbet, which is based on a sugar/water syrup with lemon juice. Tastes great with fruit (in my opinion, better than ice cream).