If the children are that young (less than 5), I would not even let them see or know about weapons yet. Even toy guns.
They would stay locked away like the real versions, as they should, until you judge the child is old enough to know about such things. At two, that's pushing it a lot.
The other thing to consider... if the kid then insists on playing, what would you tell them anyway? Wait until you are 16? Sorry, children are not that patient. We see that every day even here.
For some things, ignorance is bliss. When the kids reach around 10-12, you can start them off with some safe guns. By then they will have better coordination too, and will understand the concepts of safety a lot better.
I think a good reality check would be to ask yourself if you'd be ok to take the kid to a real gun range under supervision. If the answer is no, then they are not ready for airsoft either.