Thank you everybody and the forum founders! This would be much harder without all the free information!
There wasnt much notable about our interview experience except
1) it was much busier and crazier time of life for me then I expected, moving ones 60+ y. o. parent to a totally different country is a lot of coordinating to do, I am still not done...
2) interview was easy - officer asked my mom about me - where do I work, live and how I got my citizenship. I was sitting behind her, i donno if that helped.
3) the LAX immigration office was easy:
submit envelope to officer in booth #1 marked "New Immigrants"-> sit and wait to be called (5 min) -> get fingerprinted on a paper form -> go inside and get luggage -> come back, wait 10 more min to be called - > officer returned the passport and 1 page instruction about "wait for GC in the mail"
some other immigrants in front of us didn't have correct photos ( must be matte passport size on white background) so they stayed behind, I donno what happened to them. I suggest keep copies of stuff and photos handy.
After reading about medical insurance troubles at interview - I bought a tourist medical policy here
http://www.insubuy.com/newimmigrant.jsp but there were no questions
I donno, may be officer saw policy ID among papers mom gave him. She is not sure.
I would say my presence was most useful in the airport (and of course at traveling/packing), although they had bilingual employees - they were paged through speakers to different booth numbers,
so I am sure she would pass it eventually even if i wasnt there.