There are always potential side effects from all things consumed, you could one day first eat a peanut and die, what we need is the right to choose what side effects we are willing to risk having for the benefits of what we consume. The government have no part to play in this other than to allow legally sold with the health warning that literally anything can happen but that it is hoped that only the best effects and results are experienced......or they could continue what they already do and this is to warn us all about everything.
With regard to keeping it say from children, if you compare it to the demonic bombardment of advertising and marketing we allow our children, as well as some of our own opinions and behaviours, to be exposed to then seeing a a minority of people smoking a spliff is of negligible concern, unless the children are being forced to do themselves by evil doers.