When the messengers returned to Yaakov Avinu and reported that Eisav is on his way with four hundred men Yaakov was petrified. The Midrash comments that part of his concern was that his brother Eisav had been living in Eretz Yisroel all these years while he was living in chutz la'aretz and perhaps the zechus of observing the mitzvah of living in Eretz Yisroel would tip the scales in favor of Eisav in the event of a confrontation. But we know that Eisav was not an orthodox man; he violated many of the Torah's mitzvos. Why should his living in Eretz Yisroel be considered a zechus for him? Apparently, each one of the mitzvos is so precious and so significant that even if one does not observe all the rest of the mitzvos, the one mitzvah that one does fulfill will certainly be considered a zechus for him. It is quoted[1] in the name of Rav Yosef Chaim Sonnenfeld that perhaps Eliezer Ben Yehuda will go to Olam Habah because he was so instrumental in getting so many people to speak lashon ha'kodesh. Rabbi Sonnenfeld knew quite well that Ben Yehuda was far from being an observant Jew but nonetheless he thought that maybe the zechus of this single mitzvah alone merits one's share in Olam Habah.
Many years ago, Rabbi Mallen Galinsky z"l mentioned to me that he had a neighbor in Givat Shaul who was a descendent of a prominent chassidishe rebbe from over two hundred years ago. This person had a sefer in manuscript from his ancestor which he felt he was unable to print because readers would probably assume that the whole book was a forgery. This chassidishe rebbe from two centuries ago wrote in the manuscript that when the people from the dor ha'midbar who refused to go to Eretz Yisroel passed away and were brought in front of the heavenly court for judgment, they pleaded for mercy and asked if they could be brought back again by way of a gilgul into this world in order to rectify the sin that they had committed. After much debate back and forth, the heavenly court finally gave in and permitted them to return to this world to be misakein the aveira that they did, but only on the condition that they only fulfill this one mitzvah of yishuv Eretz Yisroel; they were not allowed to fulfill any other mitzvah. Many of the secular Zionists who built up the medina did exactly that. Who would believe that anyone who lived two hundred years ago could have ever dreamt up such a "wild idea" that the generation of the dor ha'midbor would come back in a gilgul for the sole purpose of fulfilling only one mitzvah?
Many poskim are of the opinion that one can only convert an infant if the child will be raised by an observant family and given a proper Torah education. The gemorah (Kesovus 11a) tells us that converting infants who are unable to accept upon themselves the commitment to keep mitzvos is based on the principle of zochen la'adom sh'lo b'fonov. Rav Yitzchok Elchanan[2] and many other major poskim including Rav Soloveitchik felt that it is only a zechus for the infant if he will be brought up to be an observant Jew. If the adoptive parents are not observant, we are not really doing the baby a favor by converting him but rather a disservice. Remaining a non-Jew who is not obligated in miztvos would seem to be the more reasonable choice than converting to Judaism, being obligated in mitzvos, and not observing them. The author of the Kli Chemdah visited in America briefly and was extremely impressed by the extent to which the American Jews gave tzedakah. He published a teshuva where he suggests that even if the adoptive parents are not religiously observant (regarding Shabbos, kashrus, teffilin, etc.) but the adopted child will be brought up with this attitude of the significance of tzedakah, this case also should be considered a zechus for the infant.
It is highly improper for human beings to pass judgment on other human beings. The possuk in Tehillim states, "Elokim Nitzov B'adas Keil", i.e. a beis din can only pass judgment on other human beings because we assume that the dayonim will have a Divine assistance to judge properly. We can never overestimate the value and the significance of any single mitzvah that others will fulfill.
[1] See Me'oros Yitzchak, page 681, on our parsha
[2] See Seridei Aish, Yoreah De'ah, siman 95