Yeah, but two or three climbs will probably be enough unless they really show some natural talent or are extremely strong. They'll probably be buggered after one climb.
Dam cliffs is a bit of a trek though.
The challenging start bit is a common problem with Sydney sandstone, I often find the first moves of climbs the hardest but then I'm a short arse at 5'7". I've found that my oldest daughter Daisy can often get up a route if we give her a bit of assistance with the rope for the first couple of moves of just give her a foot up artificial holds.
At Berowra cenotaph corner is an easy intro for young ones and then at a bit harder there's Marsala or Taylor Made if they're feeling stronger.
At the 'joey Carrie Bradshaw (but they might need a help to do the first move) and Ikon (same again). My 5 year old has done most of Ikon with help for the first few moves. Don't forget that kids hands are smaller and therefore holds are proportionately bigger.