Watermelon, cucumber and feta with a dressing of lime, chilli and mint.
Roasted veg and couscous works nicely. Use some red or green pesto and olive oil through the pesto. You can top with feta or goats cheese if you like. Alternatively, char grill veg like aubergine, asparagus and courgettes and mix with the couscous. A lemon, yoghurt and tahini dressing drizzled over.
Tomato salad - finely chop a small red onion, chop whatever tomatoes you like into roughly even size pieces (mixed colour tomatoes look particularly attractive but it's not essential). Chop a small bunch of parsley very finely. Mix all together. Add olive oil, sherry/red wine vinegar and generous amount of salt.
A really good green salad is a lovely thing. NOT the green salads of my childhood which were iceberg lettuce, cucumber and (bizarrely) some tomatoes! 
. I like mixed leaves, cucumber, avocado, spring onion, asparagus if it's in season. I usually de-green it with some pine nuts. Serve with whatever vinaigrette style dressing you prefer.
For dessert, I'd just make a cake.