Prawn cocktail - you could add all sorts to it to make it more of a seafood cocktail if you wanted. Crayfish tails and crab meat go very well with prawns.
Lentil and vegetable soup is always tasty, super easy to make and cheap as chips - massive pot of boiling water, 2 x ham stock cubes, 2 x vegetable stock cubes, half a sieve of rinsed red lentils, lots of finely chopped/grated carrots and a couple of chunky leeks cut up nice and small. Boil to death and you're done.
Pate with melba toast and a salad garnish.
Bruschetta - lots of different creative options available with this. Garlic mushrooms is one of my favourites instead of tomato and cheese!
Fried Camembert/goats cheese/mozzarella bites with salsa and salad.
King prawns and sweet chilli dip.
Mini antipasti selections.
Melon balls (use an ice cream scoop to make it look super fancy) and maybe puree some strawberries and raspberries to make a lovely, thick dipping sauce.
Asparagus wrapped in parma ham and cheese. My dad made this once without the cheese but made the most delicious lemon mayonnaise to go with it. Was really tasty!
Lots of salad options if you FIL calorie counts.