Playing From The Back - Why and When
The first question to ask is why we might want to play from the back?
The simple answer is to keep possession of the ball. A 50 / 50 hoof down the pitch (from a goal kick or a defensive clearance for example) is not any kind of guarantee of keeping possession, especially in kids' football, where controlling a ball that arrives out of the sky is going to be a big ask for younger or less experienced players. A clearance like that is going to be a lottery and whilst it might lead to an attacking opportunity and a territorial advantage, it also might not and in mini soccer do we really want to see lots of aerial balls and ping pong football...? No.
Contrast that with a ball played to feet, with good movement off the ball from the other players to provide options to the player in possession and you can see why the Pep Guardiolas of the world are such staunch advocates of playing from the back with a goalkeeper capable of accurate distribution. It's why he spent his first 18 months at Man City completely rebuilding his defence with players who fit that model. The good news is you can develop your players to do the same - you don't have to spent £200 million rebuilding your back 4.
Being comfortable passing around at the back, waiting for a good option to play forward, also allows you to draw your opponents out, leaving more space to play into behind them.
Having said that, it may not be right for your team. If you have players who are good at holding the ball up in advanced positions and defensive players who aren't comfortable on the ball, you may feel it's not the right thing. I would argue that at the younger ages, developing players to be more comfortable on the ball and eventually able to play from the back is where you'd want to go, but if you're coaching an older team and are looking to get results as a priority, you may just want to play to your strengths.
It's also worth noting that playing from the back doesn't have to mean playing short from the back. If you look at a goalkeeper like Ederson, he is capable of playing some very accurate longer passes and none of those are aimless 50 / 50 hoofs. They are well thought out.
And of course, there are times when we absolutely want to go long.
So the second thing to ask is when we play out from the back?
You do see coaches who force their players to ALWAYS play from the back when the goalkeeper has the ball. If that's your philosophy then go for it, but consider how predictable this makes the team and how much easier it is for the opposition to close off the options, especially beyond mini soccer where the "retreat to half way" rule no longer applies on goal kicks.
Giving your goalkeeper the task of trying to play from the back as a default, but the freedom to go longer with an accurate pass if he or she thinks there is an opportunity to create a good attacking situation or if there simply isn't a short option gives the players freedom to make their own choices and keeps the opposition guessing. If they start defaulting to lumping the ball down the pitch randomly when there are perfectly good options to keep possession elsewhere, you can just remind the players of what you'd like them to do and encourage them to be brave in doing so.
One key thing to remember is that if you encourage your young players to be brave on the ball and play from the back, there will be times when they WILL lose the ball in dangerous areas and the team will concede goals. It is inevitable, however good your players are, so it's really important the players (and parents) understand what the long term aim is here and the rest of the group are supportive when mistakes happen. Players who get shouted at or are blamed when they are just doing what they've been asked to do are much more likely to revert to "safety first" lumping the ball down the pitch.