Here's another rally drill from Lauren Stewart at The Woodlands. Again, suggested for 2.5 players but perfect for beginners of all ages. Another trait of 2.5 players is that they lack consistency. There's a drill for that. :)
Players pair up with a partner across the net and cross court. Play within the singles lines. Pairs/teams earn one point for every five ball rally achieved. First team to 5 points, wins. Switch sides (not ends) so players can get proficient on both sides of court.
If you have odd numbers of players, divide into teams and have them rotating in for whoever makes the error.
Play within service boxes with red or orange balls for easiest or for a good warm-up.
Start on 60 foot court with orange ball; progress to full court with green, then yellow balls.
Allow alleys. Two points for any ball landing in alley.