I only found out about this yesterday, but looks like a good family day out, with geek bonus points..

"Last staged in 2009, the Glenbrook Vintage Railway's Steam and Vintage Country Festival 2013 is absolutely not to be missed! Steam train rides, visiting steam locomotives, traction engines, Clydesdale horses and vintage tractors in action working the fields, vintage cars, vintage aircraft, and even steam boats offering rides on the lake! Models, vintage engines, big bands, childrens entertainment, displays, food and much more. Vintage action galore!!"

http://www.railfan.org.nz/_brochures/Steam_Festival_Poster_2013_v7.pdf

Spreading the word, as I haven't seen it advertised anywhere!