Infant and young child have been exposed to toxic black mold - it's been in our walls for months maybe years. How do I know if they're ok??

ADL. Activities of daily living.The best way to screen a kid for significant health issues is to consider their activities/eating/sleeping etc.If they act normal for their age group they likely are. There are hundreds of "dark " molds and only a few toxic ones. Individuals can have an atypical allergic reaction to any of them.Much of the lay fear of black mold is media hype. Your doc can sort it out.
Black mold. They would have significant respiratory issues if it has been a problem for them.