Frankly, the more effort it takes between shots, the longer it will keep them occupied. Children shouldn't have things too easy, unless they work out the hard way how to make things easy.
But still, it's far from efficient.
More sensible containers would perhaps be the size of an aerosol can, or a camping gas bottle, or one of those CO2 canisters that wealthy mountain bikers use to inflate tyres after a puncture.
Certainly the last of these is designed to hold high pressures, I doubt the other two are.
I think only one battery has been lost in the wild, and that was my fault (they complained bitterly about it). You're quite right, it would not be nice to litter the world with used batteries.
Daniele