Hi Lach. We love the Jamieson Caravan Park (30kms from Mansfield). It's hugely popular esp during peak times but you might get lucky in Jan if there's been a cancellation. It's right on the Jamieson River but intersects right near Foots Bridge with the Goulburn River. Great swimming holes nearby in the Jamieson River, kayak hire, a swimming pool, fishing, open fires (as long as it's not a day of total fire ban), gold panning etc.
Plenty of free bush camping places on the Goulburn River further up the road towards Kevington if you're not keen on a caravan park but again these will be pretty popular in Jan. All right in the heart of the High Country with heaps of 4WD tracks and stunning countryside. Mansfield Visitor's Centre and the Jamieson Caravan Park will be able to give you heaps of info on all the local attractions.
Sheepyard Flat is a very large, flat, extremely picturesque bush camping area with some sites that are more private and separate from the main body of camping. The Howqua River runs right through it. We love camping there and it's easily accessed from Mansfield (abt 40kms away).
Skipworth Reserve, near the Ned Kelly tree and only abt 45 kms from Mansfield, is a huge flat camping area surrounded by beautiful bush. We camped there every Easter for years when it was just dense forest, very few people knew abt it and it had no facilities whatsoever. In the end the motorbikers and the pig shooters became an issue and we started camping elsewhere. Now it is maintained and mowed with sectioned off camping sites with fire pits and drop toilets. Pretty posh! Def worth considering as still very picturesque and heaps of space for riding bikes, games of cricket etc. No real creek nearby tho so swimming is out. Sorry.
We prefer Talbotville over Italian Flat. Italian Flat is pretty small in comparison and with the camping area situated quite low down in a narrow valley (more like a cutting) and the main dirt road running parallel directly above it, we found that the huge volume of traffic using the road showered the camping area continually with dust. The creek (Two Mile) wasn't very good for swimming in when we were there (Easter 2016). Talbotville is much more open and accomodating but when we visited there it was absolutely packed! Very picturesque esp with the Crooked River running through it.
Cheers, Carolyn