you need to lay down the rules and discipline them if they throw stuff.
It seems very odd behaviour tbh, especially from the nearly 5 yr old. Have a consequence (not throwing in the bin) for the throwing that happens everysingletime they throwe something, and be consistant and ruthless in dealing with it.
Make them pick whatever it was they thre up and put it back where it goes.
The consequences of throwing need to be bad enough in their eyes to make it not worth their while to throw anything iyswim.