Okay, as I DID run games with kid PC's, the first thing I can tell you is the rules you implement depend HEAVILY on what you're trying to accomplish.
First, I ran a mixed game where there were 2 kids in the party, one PC and one NPC they were protecting. In this game, like in The Phantom Menace, the kids were exceptional (like Anakin in TPM). In this case, I didn't in any way hamper their character creation, as they were assumed to be capable enough to be on the adventure, there was no reason to set the "low" bar lower than any other capable PC. Instead, I thought of the character as a baseline to the equivalent of everything comparable. Brawn 2? Well, that is average human brawn for a kid your age. Take that Brawn 2 up against an adult with Brawn 2 in an arm wrestling match? Well, in that case, your muscle mass is lower than your opponent, so your facing an uphill battle, and I'll upgrade the difficulty once. Similarly, I took into account situations where it would work as benefits as well, such as sneaking - where kid characters actually got a bonuses to their stealth checks for hiding in a warehouse because they could get to places that the guards (who were concerned about adults) just wouldn't check. In some cases, where the kids were facing battle alone, instead of facing a Minion Stormtrooper, I used the stats for a Rival Stormtrooper, to reflect that by themselves, simple adversaries were a little tougher. This campaign was never going to last a number of years equal to what was needed to have the PC "grow up" so there was never a worry about how to adjust the stats at maturity. This made it easy to have the stats be
Now, in another adventure, I had a group of PCs that were all playing Younglings. This was intended to be a "prequel" campaign to the actual game. When I did it this way, I started the PCs with reduced experience points, instead allowing the game sessions I had planned to "fill in" these starting experience points to their normal max by the end of the prequel sessions. I had placed where each "session" of the prequel would begin and end, which, regardless of how many actual sessions it took to reach these milestones, would be the points at which that "session" of experience was released. This I did by having "life-lessons" learned at each of these pinnacle "session" endings, which then imparted learning experience equal to the planned amount. In this regard, it allowed the PCs to grow their character creation decisions through actual events, and the end result was starting PCs that reflected a deep backstory once they reached maturity. I also reduced their Brawn ratings by 1, to a minimum of 1, to allow me to run the opponents without need for augmenting die rolls. Then, when the "prequel sessions" hit maturity about half-way through, I awarded those who lost a Brawn with a free point of Brawn. Once all the "prequel sessions" were done, they then had starting point characters that I was able to match up with the rest of the PCs who weren't playing Jedi without having anyone out of balance with the others.
In both cases, the one rule that I implemented that changed normal character creation for the kids was the application of Silhouette 0 to their character sheets instead of their normal Silhouette of 1. This was necessary purely for passive interaction needs, so it was applied until they grew out of it.
