Two choices Shaun.
The entire track ends towards Scone, which is about 120km from Gloucester, much of that on dirt. It should - judging by the maps only, so reality could be wrong - take about 4 hours to get to Scone. That means 4 hours to get back again, for you guys.
The second choice - and I think this one is better for all of us - is that some of us come in from the Scone side in a group, some come in from the Gloucester side in a group, and we go back the way we came or go the other way through depending on how we want to do the trip. Polblue Campground is 2 hours from Gloucester, so that's just 2 hours back for you guys - might be better with the little guys on board.
If the Scone team departs Scone at 10am they should arrive at Polblue at noon, and same for the Gloucester group.
Looks like there might be some that are going to go in with the Gloucester and out towards Scone - really I don't mind which way any of it happens, I'm looking forward to chin-wagging over a sausage sanga at Polblue.
If we call it a day @ 4pm, you guys would be home at around 6:30pm. I think Nevyn (from Forster) may go back with you - makes sense to me.