Nope...not 'till they're @ least 5...
And possibly older, depending on the kid.
0-1: Bigtime concerns of hearing damage, noise trauma. Basically, you'd have a helpless proto-person strapped to a stroller pooping their diapers every time a round went off.
Incidentally, the startle reflex is one of the few root BIOS routines we're born with.
1-3: Once they're mobile, they're impossible to corral. Still too young to rely of them keeping their protective gear in place, this is the age they're most likely to take off down range.
If you don't think a toddler will take off downrange, then you've never had to care for a toddler.
Furthermore, their communications and understanding is extremely limited, and they can wind up with some VERY strange ideas as to what's going on.
4-5: At this stage in the game, they're getting a bit more solid, but they're still unpredictable enough that I'd not risk it.
5+: Evaluate the kid seriously, and act accordingly.