The athlete may start and stop their throw and it will not count as a foul as long as the weight does not leave their hand and as long as they do not foul with regard to the trig. If the athlete desires to set the implement down or step out of the trig area, they may do so with the judges permission. The S.A.A.A. has instituted a rule that only persons that are eighteen years or older may participate in the games. This rule came about because of safety concerns. The weights used are too heavy for children to control safely.
Many games do have children events.
These use smaller implements and are run separately from the adult events. Many, but not all athletes use hammer boots during the hammer throws. The athlete kicks the spike into to ground to anchor their feet firmly to the ground. This allows the athlete to spin the hammer at velocities that would otherwise pull them off of their feet. There are several very good calendars of games available on the internet.