Cheapest way for me and my son to go for a ride in a plane?

Hi all, me and my 7 year old son are aviation nerds and love watching planes at the airport but he hasn’t been on a plane himself since he was a toddler. I was wondering what the cheapest way would be for us to get inside a plane and fly together (as passengers) in any size aircraft. I’ve done a few trial flights in a Cessna 172 at Redcliffe aerodrome but it’s fairly pricey and you can’t take kids.

We like to spend weekends having adventures and would be down to go almost anywhere and any duration so long as it’s not gonna cost an arm and a leg. Looked into cheap flights to Mackay and Proserpine but return flights for two people just for a joyride is still fairly expensive.

Shot in the dark, maybe such a thing doesn’t exist but figured I would ask and see if I could get any ideas.

Cheers all.