Menu ideas for lite afternoon meal

Chicken salad, my favorite recipe is posted on my profile. It's light filling and great any time. BB

one of my favorite dishes is a vietnamese grilled chicken rice bowl. served at room temp. has rice noodles, salad greens, cucumbers, chicken, maybe an egg roll, a prawn and the sweet sour dressing to pour on each noodle bowl. light, flavorful, perfect on a warm day.

There are so many good soups you could serve. If it's really warm you could serve a chilled soup. There are also many good light soups you can also serve warm. I always love avegolemono. Soups are also something you can easily hold while you play tennis. Salads are an easy side or anything else you really love.

Tea sandwiches with a simple salad and/or fruit salad with cookies.

If this is intended as dinner, choose what you like and/or is in season.
If people will, otoh, be going on to have dinner, I would serve a buffet of nibble food/tapas so people can eat to various levels of hunger.
Include a fruit punch or fruit salad, for sheer pleasure and to help replenish fluids.

Quiche and a salad? I love Ina's lemon vinaigrette on this simple salad, that can be plopped on top of a quiche slice or on top of a homemade pizza: http://www.foodnetwork.com/recipes/ina-garten/arugula-with-parmesan-recipe-1944150
Individual pizzas? I never thought of lemon on pizza, but everyone I've ever served this to loves it! You could premake the dough, and have your friends all assemble their own when you get home after tennis. This recipe is an ace! (see what I did there? ha!) https://www.marthastewart.com/332431/lemon-and-piave-pizza