Keep in mind if you want to do a harbour scenic with your PPL you'll require a radar CTA approval if you don't already have one.
Cessnock is not a bad option for a quick day trip. The cafe in the information centre located at the airport has some really nice food at discounted prices for pilots. There is also a couple of vineyards with wine tasting within walking distance. De Bortolli is about a 15 min walk if you turn left at the airport gates. Go up via the central coast and cut inland near Aeropelican to keep it scenic. Come back via the Hawkesbury.
Wollongong is an option too. Always a scenic place to fly into (albeit a bit rough if it's windy) and has a good cafe at the airport. I used to get a clearance (if avail) to depart via Picnic Point through Sydney's class C which makes the trip down really quick, and then come back up the coast, victor 1 and enter at the heads for a harbour scenic then track along the Parramatta river towards Prospect to return to BK. Only risk with this flight is your flight time/cost depends a lot on getting the clearances you hope for.
Someone else mentioned Katoomba - just be aware it's a bit of a rough old strip with some nasty terrain around....