At that age, there are really only 3 important concepts:
1) How to throw by pointing your body in the right direction first
2) How to catch by rotating your arm to the ball
3) How to not ever swing a bat without a coach watching you
Your job is to figure out how to beat those first two concepts in to them in as many different ways as possible. You're building the fundamental muscle memories of handling a baseball; the key is obviously massive repetition. If you have 6 reliable sets of adult hands, this is a three-station setup that can take a chunk of practice and keeps things moving quick:
Station 1: Throwing
-Put the kids in 2 lines, with the front kid in each line throwing to an adult 'catcher' (like double-barreled action in the bullpen) Place a ball bucket in between the lines.
--Each kid throws 3-5 balls to their catcher, being coached on how to turn their body and point with the glove/elbow before throwing, then goes to the back of the line.
--Adults should roll balls back towards the bucket/lines.
--Always reinforce clear 10ft separation between the 'active' kid and the rest of their line
Station 2: Catching
-Reverse of station 1; put the kids in two lines with the front kid being thrown to by adult 'pitchers'.
--Adults throw 3-5 soft-tossed balls to each kid for catching, who roll back the balls to pitchers
--Ideally, throw softly from knees and from 15-20 feet away
--Focus first on catching balls directly at their upper body, and then force them to move glove around the clock)
Go 15min-15min with half groups, then split off the 1/3 most advanced kids into a new station
Station 3: Playing Catch
-Line up in pairs with one row of kids on foul line facing a row of kids in OF grass
--Do NOT just let them go back and forth on their own
--Start with all the balls on one side
--Call out "Ready..Aim..Throw" for each round of throwing, with Aim being the cue to get their bodies pointed in the right position
--Keep on going back and forth with the call-outs, letting everyone 're-set' each time
Do this for another 15 min, giving the slower kids another round with the individual throwing and catching, and the more advanced kids a chance to put them both together. After a few practices, you can mix in stations for Grounders and Pop-Ups, which are identical to the Catching station except with coaches hand-throwing soft grounders or tennis ball pop-ups (don't use a racket, you don't want too much loft at this level).
The key to all these drills, and the key to the age, is we're isolating one single body action (throwing, catching, fielding) to minimize the moving parts they need to focus on learning at any one moment, and maximizing the number of repetitions we can generate in an hour. Don't focus on over-coaching any one kid; keep the line moving while reinforcing the key points.