There is one thing that every experienced coach understands about youth players and I have witnessed in spades is that know one can say what type of athlete a 7-10 year old will become at 18. One clue is the fact that if their Dad is above 6' the player is more likely to develop the body size to enable them to compete in sports.One of the problems I see on the youth league level (and the HS level as well) is coaches who have "educated themselves" on hitting trying to fit every player into one mold. There are some universal principles to hitting that apply to every hitter, no matter their body type, level of play etc. I can probably count those universal principles on one hand. After that, teaching a player the best way for them to hit becomes unique to that player's skill set, body type and other variables unique to that player.
I'll take my two oldest sons for example (7 yrs old, 10 yrs old) They have different body types and skill sets. Some general background about the two:
The 10 year old has above average athletic talent (in context of baseball talent), he's long and slinder, has relatively quick hands through the hitting zone, but has average hand eye coordination when it comes to making consistent contact with the ball and his bat control is average. That's normal for kids his age. Remember, hitting a baseball is hard for grown people who are paid to do it.
The 7 year old has elite talent (in the context of baseball talent), he's shorter in statue, compact, has explosive quick hands through the hitting zone, has elite hand eye coordination and excellent bat control.
Considering the above, I cannot teach my 10 year old and my 7 year old to hit the same way. They have different skill sets and different body types. I have to tailor their approaches and mechanics to hitting to fit their body type and their skill set.
One of the constant mistakes the testosterone driven coaches we discussed earlier is to project early biological maturers as being future stars when the actual fact is many kids will mature later and often exceed the early maturers in capability even as they proceed in high school.
As one example we played with a young LH who could not get anyone out at 14. I mean he was gosh awful with zero mechanics He went on to be a reasonable pitcher in 6A high school ball then signed to play four years at Auburn and ultimately signed a professional contract. He just grew up to have the body type that could be developed.
Who can say what type of players your sons will become. One thing for certain they will undergo many changes from now through to HS graduation.