Formal:
* Sta bene? (Singular, formal "Are you all right?")
* Stanno bene? (Plural, formal "Are they all right?")
Informal:
* Va bene? (Singular, informal "Are you all right?")
* Vanno bene? (Plural, informal "Are they all right?")
Other options:
* Sta tutto bene? (Singular, informal, more emphatic "Is everything alright?")
* Stanno tutti bene? (Plural, informal, more emphatic "Is everything alright?")
You can also use "Sei/Sie a posto?" which translates to "Are you okay/alright?"
Here are some examples:
* "Sta bene?" (Are you all right?)
* "Vanno bene i bambini?" (Are the children all right?)
* "Sei a posto?" (Are you okay?)
The best way to choose the right expression is to consider the formality of the situation and your relationship with the person you're speaking to.