This is shaping up nicely. I think the characters are fine where they are so long as you make sure the contrast and saturation on them make them the focal point if that's your goal. I agree with the above comment about the stairs. To me it looks like they need to be pushed back to line up with the entrance.
Lastly, I think adding something big and close on the lower left, and maybe even overlapping the machine some, would make the image even more dynamic as if we're peeking over random shop items or tools, like we are in the adventure with the kids and they were caught but we were not. Now I want to see what happens next!
@myss Thanks for the help! Will keep your image for future reference as well.
You know... I tried a line of action a few times, but just could not get what I was after. Even tried to find some reference, but I guess my keywords weren't clear enough for what I was after. Like both you and @gubhart show, having his shoulder up and a leg bent is the key here. Thanks, again!