On a flight at the end of the 90s, the plane -- most likely a 747 -- made a stopover at an airport to refuel.
In my recollection, during the refueling process all of the children needed to leave the plane. What is the reason for this procedure?
When they have children leave the plane, it is probably a company thing! There are no such rules that all passengers have to deboard a plane during refuel (with JetA and similar). But, as you can see in the Airbus FOPN, there are some requirements that need to be met. Each manufacturer as well as each company probably has its on way of interpreting of the rules and regulations issued by the CAP and the FAA.
Summing up, it is basically by the pilots and therefore the company's discretion what to do with the passengers (or children) on board during refueling as long as saftey requirements are met!