Question

oh its just the chicks playing they will be fine---but when they get older it may be a problem because they tend to do more damage. but you dont have to worry about that now- they are perfectly fine!

 

They are probably males establishing pecking order like you said. But also look to see if their combs are growing a bit bigger than the other chicks and are their hackle (neck) feathers coming in pointed (male) or rounded (female). I mention these other things to look for because the boys aren't the only ones who play/fight like that, the girls have their own pecking order tiffs, too.