1) One may not give wine and meat even to a small child during these days (Mishne Berurah 551). There are those who are lenient regarding a child who has not yet reached the age when he can understand the idea of mourning for Yerushalayim. (Magen Avrohom ibid)
2) As regards Havdallah after Shabbos, the Ashkenazi custom is that one gives the wine to a minor to drink, and if there is no minor, an adult may drink. The Sephardi custom is that an adult drinks. (Shulchan Aruch and Mishne Berurah 551)
