L1B to H1 transfer while wife in India -- urgent

[V_G]

Experts, please help...

I am on L1B with Company A.

Company B is processing my L1 to H1 now.

Meanwhile my wife and son are in L2 visa and they are in India right now.

Here is my question -

If my status is changed from L1 to H1 (petition approved alone, will get the visa stamping next time when I go to India), can my wife and son get the H4 stamping (before I get the H1 visa stamping )and come to US?

Or will the L2 visa be valid for couple of months till they travel here?

Please consider this as urgent priority.

Thanks,