As a former mascot, your vision is very restricted in those suits. Especially your downward vision for the shorter kids. I had a few times where I basically ran a kid over because they walked right in front of me without me seeing them. So I was ready to defend the performer.
But then you watch the video and see that the performer looked straight down at the kids. Got the hand ready and started waving at them before shaking it out, shaking their head, and walking away. There is something to that that doesn't seem right. Not necessarily lawsuit level not right, but if I was that person's manager I'd be talking to them.
Having said that, we're only seeing a few cultivated seconds that the people complaining want us to see. The video cuts exactly when the child looks at the camera. What happened after that and how did the character interact with the next kid that they mention? There is likely more to the story.
The only time that I as a performer ever stiffed a kid like this was when I had previously interacted with them and they were jerks to me. Hitting me or in general being abusive. I'd usually give them a similar head shake and walk away onto the next kid. I'm not saying that this is what happened in this scenario, but if you twisted my arm and I had to come up with a non-racist reason why a performer would act this way that is what I would have thought. Those girls look pretty young compared to the kids that usually acted that way though, so I highly doubt that happened in this case.