Adding two lavatories to existing vent

I am remodeling a bathroom and want to use an existing vent pipe which currently serves only a bathtub. I want to add two (2) bathroom sinks in a 6 foot vanity. ech sink would have it's own trap goin straight back to the wall then make two (2) 90 debree turns to reach the drain/vent. The drain is a 2" galvi and reduces upward to a 1 1/2" vent (also galvi) which rises approx 8 feet throught the flat top roof.

Thanks in advance.

Do you need step by step instructions or what is the inquiry¿

Or is it a declaration¿

I want to make sure the vent pipe will handle the fixtures

Depends on the code your inspector uses. Here it wouldn't. Two inch roof penetration is required.

sinks

The vent pipe would be adequate as long as you connect to the 2" portion for the drains. Why does EACH sink need TWO 90's to connect to the main riser? That would normally be a "deal breaker" to a strict inspector.