Spanish rice (also known as Mexican rice) is really tasty. This is a good recipe for it:
Buy plenty of salsa and chips too. Tapas are popular in Spain and this would be a large platter filled with serrano ham, cheese, olives and other snacks like that. Have some toothpicks on the side so people don't have to use their fingers, and some napkins too.
Bread with aioli is nice. Although aioli is traditionally made with garlic (ai) and oil (oli) you can make a very nice garlic mayonnaise by mincing some garlic and stirring it into mayonnaise until the flavor is to your liking. Serve this with the bread.
A typical Spanish salad, if you want to make one, is a bed of lettuce leaves, topped with olives, canned tuna, canned corn, tomatoes and grated carrot, served with olive oil and red wine vinegar.