The quality of life is very poor in India especially in the last 5 years. I'm sure you know it if you are from Delhi. Though living standard has improved a bit in India but other things got miserable, and I'm talking based on my personal experiences. India is full of mosquitoes and dust. Roads are so bad and so narrow. Water and electricity go off all the time. Forget about staying in Delhi during summer time. I was in Delhi last summer and there was no water in whole daily for 4 days. The chief Minister of Delhi, Smt. Sheila Dixhit, said: "We can not do anything because we are not getting supply of water from neighboring state-Haryana". Crime rate is highest in India. Competition is so much and tough. Everyone is living in Western culture. No Indian morals and values left. I don't know if your children would like living there especially if they are born here. And if they are not born here then you can provide them a better life in the US than in India.
Your wife could still be able to taking care of parents and family in India if she becomes a US citizen and obtains OCI. She has nothing to lose. At least she could come to US at anytime she would prefer. Just you to know that I never took any money from my parents nor from US govt. to study here despite of being born here. I worked part-time to support myself. I'm not saying that your kids should do the same but I'm sure you guys can find a way to solve this. I understand each person's situation and circumstance are different. But India is not the same as it used to be.
But obtaining a foreign citizenship is not good for everyone especially in the case of OP who is interested in adopting a child in India, or those who has or wants to acquire agricultural lands given the fact that many lands in India are agricultural lands. Sometimes tax rate on worldwide income also a reason to think about obtaining foreign nationality. And more importantly, criminal consequences. If I have friend who became a US Citizen recently. He went to India recently and got involved in a fight with his neighbor over property matter wherein his neighbor filed a criminal complaint against him saying that he molested his teen daughter. He did not such but his neighbor knew people in the Police station and got police report and medical report in his favor especially when millions of rupees (crores) were in questions relating to property. He just got convicted for 15 years and after that he will be handover to US authority for another 30 years in jail in US prison and he is barred for lifetime to enter into India despite of being born there and his whole family lives there. He came here just 4 years ago and got married to a US citizen and obtained his green card and now became a US citizen. Now his whole life has changed. Under the US laws, he must be serving for 30-35 years for this kinds of crimes even if crimes were occurred on foreign lands. OCI is just equivalent to US green card. Anything you would do in India, you will be thrown out for lifetime ban. So there is something to think about as well.