I have spent the last 4 summers coaching kids from reception age to u12.
In the last two games my u8 team have played they have bowled a maximum of 3 wides and 2 no balls in each game. One of the wides was my son trying to bowl a back of the hand slower ball... Argh.
We have spent a lot of time working with the kids on bowling actions and really running in to bowl and completing their actions. At the beginning of the summer I only had 2 kids who could bowl the rest chucked it.
Batting is a very different thing because you get unplayable balls, especially on the crap wickets kids play on.
But repetition of hitting balls helps.
The other important thing I have learned is don't make a big deal out of people getting out. They need to explore the boundaries of when they can run or which balls to hit. This is why pairs cricket is really beneficial.
As for the topic... Bowling is part confidence part bluff. The kids will need to learn the bluff and also need to have the self awareness that it won't be your day every day.