i think stats will encourage different playstyles for each kid, instead of them being pretty much the same. in the character select screen there will be a tab to view character stats, and the sections will include
strength (affects damage and how fast you can kick down doors)
speed
throw power
support (affects how fast you help others get out of traps, how fast you move in smoke and how long it takes to get someone else up from being downed)
stealth (affects the loudness of footsteps while running/throwing things)
posture (effects how severe the fear affect is, shaking more and screen being darker)
here are some ideas on how these would work on the kids.
Bagger would have the highest strength stat, and has decent throw power, and mediocre stealth, however he has the lowest speed stat as he currently does. 
Brave would have high throw power, but mediocre damage, and the highest posture stat (because shes… brave) however she has a pretty low stealth stat. 
Leader would have less posture than brave, but its still pretty high. she has low stealth, but she has the highest support stat meaning she can help others out of traps and get them up faster. 
Detective has the lowest posture and strength stat, which would make it hard to aim in fights, and hard to deal much damage at all. however he makes up for this having a high support and stealth stat. and his key finding abilities. 
Scout has high stealth and speed, however she doesnt deal too much damage and has mediocre throw power, which makes her not very good in fights unless your a slingshot spammer. 
Inventor has mediocre speed and strength, but has a high support and stealth stat, he also has low posture. hes good at supporting the team with his items, but isnt the best at fighting. 