Both my petitions were approved at the same time. What do I do now? Do we have to call USCIS and let them know which visa we're going to use?

My lawyer says he'll determine that after I get a packet from the American Consulate in Mumbai. Dont know if that is how it's done. Thought someone here might be able to help. Thanks in advance.

What's the timeframe we're looking at once the petitions are approved? When do I expect a packet from Mumbai?

My husband called USCIS and the lady he spoke to said the following: if I130 gets approved first you have to proceed with that; if both get approved at the same time you will have a choice.
Both our cases were approved yesterday; he will be calling them today to advise them that we wish to proceed with the K3 (I129F)

What if we dont call USCIS? Will I have a choice at my interview?

The two processes are different therefore you need to decide beforehand. If you go I130, the NVC communicates with you or your agent and submission and requests for documentation is done directly with NVC. The case stays with NVC longer, then comes to embassy, embassy schedules you for interview for CR1 (immigrant) visa. Some people report a delay in scheduling at the embassy for this. If you go I129F, case goes from service centre to NVC, stays there for approximately 2 weeks, then to embassy. Requests and submission for documentation is done directly with you and embassy. Interview is for K3 (tourist) visa to be in US while awaiting finalization of immigration case. Interview is scheduled in shorter time.

Thats my understanding.

First you need to know which case or if both cases were sent on to NVC. The I-129F/K3 case will proceed through NVC without input from the petitioner or beneficiary, but you want to verify (by calling) that they got the case file and forwarded it. The I-130/CR1 case requires interaction between NVC and both the petitioner and beneficiary, so your choice of whether to respond and among other things, pay the immigrant visa fee to NVC, becomes your choice of visa path.

If only one case gets forwarded, your choice was made for you. Since November 2006, USCIS's policy was to hold the I-130 and send only the I-129F to NVC. They've made some unannounced changes lately, so it is unclear just what they will do when both petitions are approved together at the present time. Many are impatiently waiting to find out.