Wow, as someone who works in customer service I am completely amazed at the attacks tossed onto the OP. I run multiple retail chains and I can tell you honestly, if any of my staff allowed a customer to wait for something for 40 minutes, failed to deliver the product they waited for then didn't do their best to make sure at least a smile was given, then yep they'd be back in training fast. Yes there are things out of our control that we can't do for the customer but it is our job to make sure that at least we handle the situation in way where the customer leaves understanding that we did our best. It's not about spoiled children and entitled parents, it's about customer service.
To me it doesn't sound like the OP expected anything in the way of compensation, more that they were distressed at the way the situation was handled. Yes, the CMs can not control Snow White getting sick, but they can control how they handle the situation from that point on. Leaving them standing there for 40 minutes with no updates or explainations then simply shrugging as a 3 year old cries is not an example of good customer service regardless if it's Disney World or
Walmart.
We are talking about a toddler here, not a grown adult, and sometimes the smiles and good words from someone other than mom and dad are the perfect cure. Toddlers don't understand adult events, they don't understand Princesses get sick or can't "work", they just know they waited for Snow White and now she is not coming...cue meltdown. It doesn't make them a brat, it makes them a 3 year old. A CM getting down on their level and saying, "Sorry Snow White had to go help wake up Sleepy for work, but she told me to tell you hello and that she will hopefully see you later and she is so proud of how patient you were waiting..." would have gone a long way probably. Customer service doesn't always have to involve tossing out a comp and customer disapointments don't always equal entitlement.