Eruvin for Minors – Eruvin 30a
ב"ש אומרים אין מערבין לנזיר ביין כו' ב"ה אומרים מערבין לנזיר ביין אמרו להם בית הלל לבית שמאי אי אתם מודים שמערבין לגדול ביום הכפורים כו' כשם שמערבין לגדול ביום הכפורים כו' כך מערבין לנזיר ביין כו'
Beis Hillel's position is that the Rabbinic decree of eruvei techumin is uniform. Hence, although an adult may not partake of the food of the eruv on Yom Kippur, the eruv is nonetheless valid, since it is suitable for a minor. Similarly, although a nazir may not partake of an eruv of wine, it is nevertheless valid for him since others may partake of it.
The Ohr Somayach (Hil. Maachalos Asuros 17:27) notes that this position seems to conflict with the position of the Rashba that a minor is not subject to Rabbinic prohibitions, and that therefore it is even permissible for an adult to deliberately feed a minor a Rabbinically prohibited substance. If so, queries the Ohr Somayach, a minor is not subject at all to the prohibition that the eruv is meant to permit. [Thus, making an eruv for Yom Kippur on the basis of a minor's potential to partake of the eruv would seem no better making an eruv on the basis of a non-Jew's potential to partake of the eruv, which is definitely not effective.]
In the end, however, the Ohr Somayach reconciles the position of Beis Hillel with the position of the Rashba. He explains that although the minor himself is not personally subject to the prohibition of Techum Shabbos in the sense that he is held liable if he violates the prohibition, the techum of all his possessions are subject to the techum. Hence, were the minor not to participate in an eruv techumin, all the objects he owns would remain forbidden to exceed the two thousand amos of his original techum. Indeed, posits the Ohr Somayach, it would seem that an adult is forbidden to move the minor beyond the child's own techum unless the child participated in an eruv. Thus, the minor may not be obligated to participate in an eruv techumin, but he is subject to one, and therefore he may serve as the basis for an eruv on Yom Kippur.