Always have an "early arrival" or "late pick-up" activity table. It helps keep the players from feeling alone and connect with others in the same boat. Let the players know this area is there for them anytime they have idle time on their hands.
Have paper, chalk, pencil, coloring pencils, and ideas on a board for kids to play on. Please provide them with coloring pages or something they can take with them at a moment's notice. Leave a sample for them. Make a paper airplane, draw a giraffe, and have a Hangman game, Tic Tac Toe, Box, and Dot game ready to play with a friend.
Post the lesson's vocabulary sheet nearby and encourage them to use this in their games.