chicks-when to intergrate?? holiday advice

my chicks are now 6 weeks old and fully feathered.we have lost two but the other seven doing very well and eating all in sight.they are in a smaller run inside the big chicks run with a rabbit hutch to sleep in.their mum is still with them but they can see the other chickens.when do i separate their mum or do i just let them all mix together??we are going away for a week in  two weeks time and my neighbours son who used to have lots of chickens is going to visit am/pm to feed and let in/out of coops.i would feel happier leaving them in their separate run until after we get back when they will be 9wks old ,is that ok???
i,ll try to sort out pictures of them at weekend as i would love some of you clever lot to try and sex them for me