My go to if I've got a lot of people round in the summer is...
A big bowl of salad leaves plus tomatoes, cucumber, coleslaw etc
Some pasta or potato salad or boiled new potatoes
Salmon cooked earlier in the day or the day before
Chicken pieces stuck in the oven as needed
A few sausages for the kids (again stuck in the oven)
A nice selection of vegetarian flans or vegetarian 'chicken' fillets
Lots of different breads/rolls plus butter
For dessert I do 'deconstructed Eton mess' which is basically a big plate of meringues (shop bought, I'm not spending time on those), a big bowl of mixed berries, big tub of very good quality ice cream and a big jug of double cream. That way, if people can't have cream they can have bowl of meringue and berries, if they don't like berries they can leave them out and kids can have a huge bowl of ice cream. I get some sticky ice cream sauces too so they can help themselves. Less work, stick it all in bowls then on the table and they can make what they want with it.