My husband makes kiddush on a full becher of liquor (he has wine but prefers to drink liquor) on shabbos morning. Since the children (the oldest is 8 years) can’t drink liquor he gives them each a small becher (less than a reviis) of grape juice and has them make kiddush along with him.
Can you explain what is halachically incorrect in this situation so we can correct.
It is fine to make Kiddush on liquor if this is the preference of your husband (see Mishnah Berurah 272:30).
It is also fine for children to drink from their own cups. As the Shulchan Aruch Ha-Rav (190:5) writes (see also 271:29), although there is a mitzvah min ha-muvchar that the attendants should partake of the wine at Kiddush, they can do so from their own cups.
The problem, however, is that your husband is making the wrong berachah for the children’s grape juice.
This is why your husband gets the children to make their own kiddush, so that they say their own berachah — hagafen, rather than shehakol.
But this is also problematic, because their cups contain less than a revi’is. Eight years old is possibly chinuch age for berachos (poskim generally say approx. 9), so that a cup with a revi’is should be used.
An interesting solution is that your husband should make kiddush from a grape-based liquor, whose berachah is borei peri hagafen (I am not sure that there is such a thing), and the children could then hear your husband’s kiddush (without joining in), and proceed to drink from their cups of grape juice.
Best wishes and hope things work out . . .