Depends on the frequency, whether it can be preventable with other interventions earlier, and whether it's linked to any other existing conditions they can check for. All this article has is a link to an individual story, that while scary, is not conclusive. All the articles I can find suggest it's rare and only offer circumstantial evidence it's caused by COVID.
Definitely rare... the article itself says there are only 200 known cases so far across the US and Europe. But if you're a parent, are you willing to take that risk with your children? (General "you", not you specifically.)
And yes, there's still a lot we have to learn, as with COVID-19 in general. The CDC appears to believe that MIS-C is associated with COVID-19, though.
https://emergency.cdc.gov/han/2020/han00432.asp