I have been coaching my son since he could first play, from T-Ball all the way to now Kid pitch
The best advice I can give you for coaching that young is to get them to understand where the bases are and where you need to go with the ball. Too many times I see kids out here that don't understand what they are supposed to do with the ball.
Throwing fundamentals and hitting fundamentals will come as they get older and get those reps.. just a basic understanding of what you need to do with the ball seems to be the biggest obstacle I see with kids out in little league. Running through first base, not slowing down and stopping on the base. Pretty much, teaching them HOW to play the game will make the biggest impact as they move up.