I would think about some things that you can perhaps do in advance and freeze or put in the fridge then make up at the last minute. Another option would be to get some ready made stuff that you can add to so that it's different and to make it your own.
Here are some ideas for you:
Salads - sliced plum tomato, fresh basil, thinly sliced red onion, black olives, olive oil and freshly ground black pepper (you can also include slices of mozzarella or avocado).
Mixed salad leaves (baby spinach, rocket and watercress are nice although most salad bags are fine), sliced ripe nectarines, parma ham slices, mozzarella (get the fresh buffalo mozzarella and pull bits off rather than slice), this can be drizzled with a little olive oil or a kind of vinaigrette dressing if you would like.
Ceasar style salad - cook chicken breast in advance and cut up, cut up some bread and fry in olive oil to make croutons, grill or fry some bacon until crispy and break up, use some gem lettuces (or other leaves if you prefer) and take off the leaves then mix them in a large bowl with the chicken, bacon and some black olives and some bought fresh ceasar salad dressing (a bit of a cheat but makes it easier!) when mixed serve it with the croutons on top and add parmesan shavings if you want.
Roast or grilled vegetable salad - roast or grill a mixture of veg (e.g. peppers, courgette, aubergine, red onion, squash, asparagus) and serve, either warm or cold, mixed together with a dressing made from balsamic vinegar, olive oil and seasoning.
You could serve an Italian or continental style platter with bought ready sliced meats and salamis, antipastis (e.g. marinated olives, roasted peppers, artichokes, etc), tapanades, different breads and cheeses - all you need to do is buy the stuff and put it out.
Skewers or kebabs, that you cook on the grill or can barbecue if you decide to do that and can be made up in advance - you can put lots of different things on, prawns with a thai style marinade (chillies, lime juice, fresh coriander, lemongrass, a little oil), chunks of vegetables marinated in balsamic vinagar, olive oil and herbs, pork and apricot, lamb and aubergine marinated in yoghurt with spices such as cumin, coriander, turmeric, cloves, etc.
Desserts - Eton mess with either strawberries or raspberries, the fruit can be prepared slightly ahead of time (if using strawberries cut and wash then put in a bowl with some sugar, leave for a couple of hours and you will have a syrup with your fruit) as can the broken meringues (put in airtight container) - before serving, whisk some whipping cream, mix in the broken meringue and strawberries with their syrup and serve in small bowls garnished with a bit of fruit and sprig of mint.
Roasted peaches or nectarines served with crushed amaretti biscuits and creme fraiche or mascarpone.
Hope that helps. There is plenty more you could do!
Helen