The small children must be given the Holy Eucharist as often as possible, because the Holy Eucharist strengthens the body and soul. Of course that the babies must be breastfed before the Holy Liturgy and it is allowed to be given some food to the small ones.
The bigger children will commune on an empty stomach. The earlier will appear the feeling of awareness of the communion on an empty stomach, the better. After the age of seven the consumption of any food or drink before the Holy Commnion is forbidden.
Source: Pr. Prof. Gleb Kaleda, The church from home, Sophia Publishing, Bucharest, 2006, p. 66 via doxologia.ro