Hi Kylie,
Beeripmo does have quite a bit of up and down but none of it goes on for long and if the weather is clear there are lots of opportunities to stop and admire the views.
We took our younger two for their first overnight packwalk (they carried!) at ages 5 and 7, so we started rather late in age which had more to do with worry on our part - in the end they coped admirably. We kept it short and simple because we were running so late that we didn't start walking until sunset. We parked at Mugwamp Camp and then walked up to the Beeripmo campsite, which was about half an hour. If we'd started early in the morning, I'm fairly confident they could have done the entire Beeripmo walk, with plenty of time for breaks, snacks and stopping to look at nature. It really does depend on your kids and their prior walking/camping experience.
There was a bit of discussion on using Beeripmo as an intro walk for kids on another post:
http://bushwalk.com/forum/viewtopic.php?f=46&t=1122&p=172538&hilit=beeripmo#p116040Our kids had already done quite a few 5-10km day walks and also bush car camping, so for us it was about putting the two together. They each carried their own (school) backpack with a jacket, their water, some snacks, their headlamp, and a change of clothes. One also insisted on carrying her teddy bear. Carrying their own gear was one of their highlights! From memory, their packs were about 3-4kg so much, much less than 25% of their weight, but for younger kids I'd probably just get those drink bottles with the snack container on the bottom so they can eat and drink when want also get to feel a bit independent. Again, it depends on what your kids are already used to doing.
Enjoy!
Simone