Well that's a lot of really good information. There are signs up around the habitat to not "chase" the kangaroos and that last bit is probably why. They mostly seem to be very mellow, but if their food is being brought and they're being taken care of, they may just have no worries.
Are you certain they're red kangaroos? In my experience at least it's usually the eastern grey species that are kept in walkthroughs due to them being more naturally docile.
It's one of the reasons I was hoping for the eastern grey for the Australia Pack (along with the emu). Many zoos here in NZ have eastern greys and emus in walkthrough habitats together (and Bennett's wallabies).