Okay, the visiting children issue is its own separate problem. The idiot barstaff wandering off to dance rather than work is, again, its own separate issue. We've had that annoyance in every iteration of the Sims. It's somewhat of a "Tradition" now.
But yes, the problem with autonomous sims continually ordering drinks and getting none is very much connected to your own sim then having a similar problem. When you see the crowd failing to get drinks, order after order, that is exactly when you own sim will order, the money is taken, and the barstaff will attempt to serve. Notice how the barstaff will only attempt to serve your sim. All others, despite their endless demands, and the barstaff does not flinch. But with your sim the barstaff at least tries. They bend down, grab the mixer from below the bar, then go straight into the route fail animation, left hand raised and waving while holding the mixer. Then back to standing there doing nothing. In every instance when this occurs, I go straight into build/buy mode and start pruning away nearby objects. I DO NOT reset the barstaff. I DO NOT reset the bar. I DO NOT replace the bar with a new one. I have learned this can crash the game. I do however grab the bar and any connected counters and move them around, then place them right back where they were.. Then I simply prune away nearby objects and try to buy another drink. Eventually, and in every single case, the barstaff finally is able to serve my sim and all other autonomous sims. Even when I return to the bar on another day, it is working as it should. If and when, of course, when the idiot barstaff stop dancing and chatting and remember they are there to actaully work.
PS I always, always, always click on the bar to order drinks, and eventually, after enough objects are pruned away, it finally works.