The heritage line was forced to suspend steam and replace locomotives with diesel in July after cinders from engines sparked several lineside fires in dry conditions.
Following rain since the start of the month, it has been decided that it is safe to run steam again.
And the attraction is allowing children aged 4-15 to travel free for the remainder of the school holidays.
General manager Chris Price said: “Working with our local stakeholders we took the decision last month to supplement our steam locomotive fleet with diesel engines assisting our trains, to minimise the risk of further fires.
“Now that we have finally had some rain, it’s great that we’re able to go back to our full steam service for the remainder of the summer holidays.”
The free child tickets are available from August 8 until September 4.