There are definitely challenges. IMO, mostly related to 13-14 year-old boys playing a man’s game on a man-sized field. They run slower, they throw slower, they swing the bat slower, they react slower. You will probably see huge developmental differences amongst kids in this age group. Party due to age, and partly due to levels of maturity. I think the transition is less about experience and more about getting physically bigger and stronger. Be warned, it may be painful to watch for a while, especially if they’re required to swing -3 bats. Don't be surprised to see Infield In for the whole game. But it’s all part of the process, and it's still baseball. They’ll figure it out.
A word of caution about pitching. My son was bigger and stronger than most of his teammates at 13U. That made him a favorite with his coaches for pitching. To compound the problem of pitching too much, he also started developing better control which allowed him to throw with more effort (he couldn't throw max effort at 12U and still throw strikes). I didn’t know enough at the time to protect him and he ended up with elbow problems.
On other thought on catching/blocking. It's even more difficult at this age. In high school, the catcher pretty much knows where the ball is going, so he's actually working with his pitcher when it comes to blocking. At 13U, the pitcher is throwing the ball all over the place. The catcher might have to block a FB off the plate and in the dirt that he was expecting down the middle. Much tougher on catchers at this age.