I've started hiking with my 5 & 3 year old daughters, so I carry all the gear. On our first overnight walk to High Camp Hut (on Mt Anne/Eliza track) this meant carrying around 25kg, quite a load especially as I sometimes end up carrying my 16kg 3 year old. So this ultralight hiking business got my attention and thanks to all the good information out there, with a bit of thought and money later I'm now getting around the 12kg mark including food & water or just under 9kg base weight (so we even sneak into the official light backpacking category!) It's pretty neat that all the gear for the three of us weighs less than many other folks carry for themselves. It was also very eye opening to realise that it was even possible to start going on these trips with them!
The key changes are better packing of food and clothes and the following gear:
Pack
Was: 3Kg One planet 85L
Now: 0.95kg Granite Gear Crown VC 60L
Tent
Was: 4Kg Kathmandu 4 season
Now: 1.5Kg Big Agnes Angel Springs UL3
Sleeping bags
Were: Assorted ~4Kg for three
Now: Brooks Range Alpini 30 - 0.65Kg each / 1.95Kg for all three of us
Sleeping mats
Were: Assorted ~2Kg for three
Now: Therm-a-rest NeoAir XLite 0.35Kg each / 1.05Kg for all three of us
Stove
Was: Trangia 1.2Kg plus 100g fuel bottle
Now: Trail designs Caldera ~0.3Kg including pot & pan
Our clothing is still on the heavy and bulky side, but with kids growing out of things so quickly I don't think they will get fancy UL gear for some time yet! If it wasn't for the necessity of having to carry gear for the kids I don't know if I would have invested the time & money to lighten my load, but I think this will change my enjoyment of hiking immensely even when the kids can start carrying some of their own gear.
Oh, and I was absolutely amazed at the US/Oz price difference. I would have preferred ordering from Australia, but with a US website half price or less for most of the items, and then offering an extra 20% discount and free shipping it was simply not an option.