They called the police in a situation where the need for police is implausible. There were parents there, yes? I assume they were sober. Why didn't they manage the situation as might mature adults?

No, they escalated to state intervention, and that means question of equal accommodations can be raised, if the state has laws mandating them.

But it also raises the question of racism, especially if that was the only black family in the group.

Racism doesn't merely exist in the US, it's the dominant culture right now. So yes, it's entirely appropriate to expect it and catalog when it happens.