It's late, I'm still up because I can't sleep, so how about a scouting break down for you? This is probably all stuff you already know, as you get to watch them everyday, but I'll offer it up anyway.
Isiah's game is pure speed. He's faster than just about anybody who steps on the field with him. He's not particularly powerful but you aren't gonna get him down with an arm tackle either. His vision is about average for his age group. Looks like a guy who will excel until the speed catches up with him. Unless he's Chris Johnson, there will come a point where he's not just that much faster than everyone else and then he'll need to have developed other skills to continue being a star. **Note** That doesn't mean he's a bad player. He could likely parlay that speed into a very nice role at virtually any level. Just that he'll need other parts to his game to continue being a "star".
Josh is the better runner of the two. He's not as fast, but he's both more elusive and more powerful. He also has excellent vision for someone in his age group. He's the kind of kid that if properly developed, could hit the big time some day. When he starts playing in more pass-centric offensive schemes, you make damn sure he doesn't ignore the pass protection side of being a RB. Being an excellent pass protector will exponentially accelerate how quickly he gets on the field each time he makes a jump in competition level.
Both of the little guys have got a ton of "want to", which is more than half the battle at their age. Both seem like little football playing dudes! And both appear to have well above average football IQs for their age group, I'm sure that can be attributed to their influence. It looks like you've raised a couple exciting to watch football players, you should be proud. Let us know how they do at the Youth Bowl.