I was told you can file multiple petitions as long as they are in different categories.
ie you can file a eb3 and family based at the same time.
But you cannot file 2 EB3s or 2 family based. When one is approved, you cancel(or withdraw) the other. If you do not withdraw, it will be cancelled, since the IO will see that you already have a GC. The A# in both applications should be the same.
There was another poster called vanlily(or something similar who went thru the same process till its conclusion I think).
We are in the same boat and filed family based without doing anything to the EB3.