I would record the kid on a cell phone and then standing there dial (or pretend to dial) CPS and ask for someone to come take care of the child as you have video of him/her crying nonstop for an extended period of time with NO one even attempting to care for him. Heck, call 911 for an abandoned child.
Trust me, this will stop the problem far more long term than announcements, etc.... If the boss fusses at you, tell them you are a mandated reporter because your volunteer work and you don't want to go to jail because someone finds out you didn't report clear neglect.
Don't BOTHER to be quiet when you make the call standing near the child. It will likely scare the begeebers out of some parents, then at least while you are there they will behave.
I have been in some big thrift stores, even a goodwill that was about an acre in floor space for shoppers, but hadn't heard of ANYONE spending a full day there. Must be the new thing for some reason.
Heck, if my mom had EVER heard of either gfgbro or I doing something like that? We would NOT have our children any more. She would take them and flat out refuse to give them back, telling us to call the cops if we wanted. Dad would then take us out and beat some sense into us - and he did NOT hit us after age 6 or so for me and only older with gfgbro when he flat out got up in his face and refused to comply with all other discipline. Even now I am pretty sure he would beat me for that.
As for your coworkers, how on earth do they function if they can't tell sarcasm from the real world?
I would NOT announce the free kitten/espresso thing because now so many kids get energy drinks even when they can't drink from a sippy cup. Last week I heard a mom griping to the checkout lady because WIC and foodstamps wouldn't pay for the 5 hr energy that her baby "needed". Kid was maybe one, and dear mommy poured a 5 hr energy in his bottle right at the checkout!
When the cashier (a lady I know and like) told her that she was nuts and it was NOT good for the baby, the mom said that it was healthy because it was "decaf" and this way he didn't need a nap or to sleep as much at night so they didn't have to stay home because he was asleep. She also griped because the most popular restaurant and bar in town made her leave at 10 because the rule is no one under 21 after 10. The cashier and I both were dumbfounded.
I swear some people think babies are pets. I just hope this lady never needs her kid to care for her in her old age. though part of me hopes the kid does and treats the mom like mom treated him as a baby, Know what I mean??