lamb fillets on the barbeque are delicious. marinade them first in something - garlic and olive oil and mint is good. serve with something like a couscous, my fave recipe below. then also do a tomato salad (either plain tomatoes cut thinly and dressed with olive oil and balsamic, or something like a greek salad), and if you feel like it some roasted vegetables (courgette, aubergine, garlic, mushrooms). both the veg and the couscous can be served warm rather than hot (they taste nicer that way I think).
don't do a starter, or if you do, make it something like smoked salmon on soda bread, lots of it, lots of lemon, piled on a platter and served with drinks to begin with.
for pudding make some meringues, strawberries and cream.
whole thing super easy - salad, veg, couscous and meringes can be done in advance, just need to slap some salmon on bread and stick the fillets on the bbq or in the oven for 20 mins. yummy yummy
(mycouscous recipe: look at box and see how much you need of couscous and liquid (varies alot between brands), and then for 6-8 people I stir into that dry amount a teaspoon of cinnamon, a teaspoon of ground coriander, half a teaspoon of ground cumin. then I make the couscous with vegetable stock (marigold) as normal (ie pour it over and slam a lid on the bowl), and once it is done stir in a tin of chickpeas and a load of toasted pinenuts. and some chopped parsley if you are feeling energetic. do all that in advance and before you serve it blast it in the microwave for a couple of minutes. doesn't matter if it isn't piping hot - warm is good.)