According to this post it does get adjusted for children.
https://www.dansdeals.com/more/coronavirus/coronavirus-stimulus-benefits-house-senate-now-voting/
"The checks will be phased out for single filers making more than $75,000 and married filers making more than $150,000 AGI. That amount is phased out at a rate of $5 per $100 of income until a single filer makes $87,000 or a married couple without children makes $174,000, at which point it is completely phased out. The phaseout with children will be $12,000 higher per child, so a couple with 2 kids will phase out completely at $198,000. A couple with 4 kids will phase out completely at $222,000."
This is the way it's been portrayed all over, but it's confusing. The phase out always begins at 75k/150k regardless of how many dependents you have. This is the how it was the first time and this is how it is the second time. Because it phases out $5 per $100 of additional income, if your potential check before the phase out is higher because you have children there is more room until the phase out finishes.
A couple will get $1200 less than last time regardless of income, if you got $1200 or less last time you get $0 now.
A couple with 1 child will get $1100 less than last time (-$600 per adult. +$100 per child), if you got $1100 or less last time you get $0 now.
A couple with 2 children will get $1000 less than last time.
Etc.