Hi Joannie
I'm going to assume that people don't want to be cooking stuff but that you want to be able to go to a supermarket and just buy a load of stuff suitable for your visitor (let us know if someone is prepared to cook from scratch and I'm sure we can come up with suitable recipes). As lactose intolerant means no milk or cheese, can we can assume that a vegan lunch would be alright ?
Tortillas and pitta breads don't contain milk (at least the one's I've always bought from T--s-o's don't !) - they can be the carb part of the lunch, esp nice if served warm.
Hummus (chick pea pat�) should be vegan, as should be a three bean salad. There is protein in the chick peas and the beans, so they are both nutritious dishes. You might want to check with your visitor as to whether s/he will eat quorn or soya burgers (I'm veggie and dislike both but a lot of vegans/veggies are happy to eat them). As others above have said, include a salad bowl, rice salad, couscous salad or tabouleh (cracked wheat salad) if you can get them, plus plenty of fruit for pud. Bananas are good to have too for the extra carbs.