Mr Bennett said the children had been delighted with the new viaduct recently built at Memorial Park.
"There have been lots of smiling faces."
Locomotives had been brought to the convention from all over New Zealand and even Australia.
Small railway models had been on show inside the Queen Elizabeth Youth Centre. The convention is held every two years. The last time it was in Tauranga was in 1998.
Natalie Boeyen brought her children Sam and Chloe, both 9, to the convention to ride the trains and tractors and check out the models.
"We're from Auckland but my mother lives in Katikati so we regularly bring the kids for a ride on the trains. My mother knew about the expo so we thought it would be an excellent opportunity to see a few more."
Chloe and Sam said the train rides had been their favourite.