Dear Sri.prasad, Greetings.
I am not a traditionalist, and i believe I am moderate in my outlook, but even to me this seems so funny at so many level.
Poonal for this child? really, what gothram, what lineage.
Why the muhurtham in rahu kalam?
I am assuming here. There is a very good possibility, that the mother is very bitter due to her experiences. Usually nobody choose to go through a divorce. Chances are, divorce may have been shoved down her throat by few heartless people. Quite possible, she had a very bitter resolve against all tradionalists. I know one or two very personally. It is quite possible she wanted to show someone she could do it; and chose a 'non-Indian' insemination. My assumption is based on your indication that the function was timed during 'Rahu Kalam'; but just like any other assumptions, this could be wrong.
Some of the posts in this thread are quite disturbing. This thread is all about the child's upanayanam and Gothram etc. It has nothing to do with the mother of the child. Before passing any judgement against that lady, we have to think about our own community. Can our community widen their thinking further? Can our community become more acceptive? Can our community accept there can be persons who are not quite traditionalists? Personally I said 'yes' to every question. this is despite the fact, most persons would not even consider me as a Tamil Brahmin person.
So, who taught the 'Gayathri mantra' to the child? Usually father does it. Did the mother do it? or the Iyengar did it in the place of 'guru'? I have a feeling, that lady may have chosen the gothram of her father ( I request Sri. Prasad to confirm this, please).
What is so important about Gothram? Yes, it shows the heritage. My question is, what happens in the heritage is not known? What if both parents are not known?
If we believe in God, God is common for everyone. God would not isolate one particular caste or creed for blessing. Blessing may be awarded based on one's good deeds. One may keep saying it is good karma to get the birth as a brahmin; but it is not due to bad karma if one did not get a birth in the brahmin caste.
If we can treat everyone nicely without any judgement, it would be very nice.
Cheers!