Hyatt Regency Syndey:
I thought this was a great location for families and the location was the biggest selling point for us. We were traveling with 8 & 9 year olds. We are a family who likes to have annual memberships to zoos, etc so we can go just for an hour or so and not feel the need to see everything and get our money's worth. We found the Merlin annual pass to Wildlife zoo, Sealife Sydney Aquarium, Madame Tussauds (would never go without the pass but the kids enjoyed it), Sydney Eye Tower, (and Manley Aquarium, etc) at $50USD served our purpose fine. Wildlife is not the Taronga but that was fine with us since my kids got to see all the animals they wanted to see at Wildlife. It was awesome to have a direct passage from inside the hotel lobby to these sites. We would spend the AM exploring, return to rest, then go to one or more of these sites for an hour so before they closed at 5-6pm.
We felt that transport in Syndey (even the $15AUD cap/person/day) was steep and liked the central location to many sites in the CBD, including Hyde Park. It was also an easy walk to many of the less expensive eateries. We enjoyed grabbnig food from the high end Westfield food court and having a picnic in Hyde Park. We also took the 333 bus from Hyde Park directly to the Iceberg pool at Bondi beach (it was a simple and inexpensive route.)
You can also walk south around the harbour to get to Darling Harbour Children's Playground and never have to cross the street.
I was told the south intersection (Sussex and Market) can be dangerous because this is where cars enter the highway, so be careful with the kids here.
I was surprised that there was NO pool