https://www.youtube.com/watch?v=XDwFdR4gluQ
Mike Candrea bucket work! You can use this drill for many different situations, but mainly work on feet work, catching the ball out front and moving through the ball. At this age, repetition, repetition, repetition!
Love this, this is one of my top 3 drills. At lower ages you may want to really work on form first and in that case I would point you to these 2 videos;
1. Infield progression (starts at 3:20) - We do this even at an older age to remind them about the basics again, we do it indoors with small squares of painter's tape to mark the triangle. You may want to do it every practice to start.
https://www.youtube.com/watch?v=rmJQoLK4Vos
2. Then work on just fielding
https://www.youtube.com/watch?v=CTWKhoJbzm4
Then do a throwing progression, then progress to doing everything at once (Mike Candrea). Do it every practice and this will become second nature. I always felt if you ask them to do everything to start, it's a much harder and longer road because you are accepting bad form to keep the group and practice moving. Progress to full infield with runners and balance the time at the different steps as needed. I am a huge fan of progressions for almost everything.