In Yaakov's gift to Esav, there appears to be a break in pattern. In general, it is male and females which are given, so as to propagate the gift. Yet by camels, it is 30 nursing camels and their children. As least according to the peshat explanation of Rashi. From Bereishit 32:
בַּנָאֵיהֶם, those who impregnate them, but the Torah was using clean language.
I am no expert in animal husbandry, but I would offer the following suggestion. Female camels typically give birth once every 2 years, to a single baby camel. The period of gestation is 13 months. Presumably, the presence of young causes the camel to lactate. And finally, lactation begins to decrease in the 6th month of pregnancy. See for example here.
I would suggest that the purpose of these camels was to provide camel milk. Thus, they were גְּמַלִּים מֵינִיקוֹת. One would need to send their babies with them, firstly so as not to deprive the baby camels of milk, but presumably to keep up the lactation, which was the whole point. Thus, וּבְנֵיהֶם.
And why no adult male camels? If the whole point of the camels was camel milk, and in the 6th month of pregnancy lactation begins to decrease, one might want to keep adult male camels away from them as long as possible (until lactation stops, at which point one wishes to get the female camel pregnant again). Thus, uniquely for these camels, no adult males are given.
That would be my partially-educated guess.