At a mitzvah meal such as a bris, pidyon haben, or conclusion of a Talmud tractate, one is permitted to eat meat and drink wine during the nine days, even before noon on erev Tishah beAv.
מִנְהָג בְּכָל יִשְֹרָאֵל שֶׁלֹּא לֶאֱכֹל בָּשָׂר וְשֶׁלֹּא לִשְׁתּוֹת יַיִן בְּתִשְׁעַת יָמִים שֶׁמִן רֹאשׁ חֹדֶשׁ עַד לְאַחַר תִּשְׁעָה בְּאָב, וְאָסוּר אֲפִלּוּ בְּתַבְשִׁיל שֶׁנִּתְבַּשֵּׁל בּוֹ בָּשָׂר אוֹ שֶׁיֵּשׁ בּוֹ שֻׁמָּן. וַאֲפִלּוּ בְּשַׂר עוֹף, אָסוּר. וְאַךְ מִי שֶׁמַּאַכְלֵי חָלָב מַזִיקִין לוֹ יָכוֹל לֶאֱכֹל בְּשַׂר עוֹף. וּלְצֹרֶךְ חוֹלֶה, הַכֹּל מֻתָּר. וּמִכָּל מָקוֹם אִם אֵינוֹ קָשֶׁה לוֹ, יֵשׁ לוֹ לְהַפְסִיק שֶׁלֹּא לֶאֱכֹל מִן ז' בְּאָב וּלְהַלָּן. וְכֵן נוֹהֲגוֹת קְצָת יוֹלְדוֹת לְהִמָנַע מִבָּשָׂר וְיַיִן מז' בְּאָב וָאֵילָךְ, כִּי בְּאוֹתוֹ הַיּוֹם נִכְנְסוּ הָעוֹבְדֵי כּוֹכָבִים לַהֵיכָל (כְּדִלְקַמָּן סִימָן קכ"ד סָעִיף ב'). וּבִסְעוּדַּת מִצְוָה, כְּגוֹן מִילָה וּפִדְיוֹן הַבֵּן, וְסִיּוּם מַסֶּכְתָּא גַּם כֵּן, מֻתָּרִין בְּבָשָׁר וְיָיִן. וְחוּץ מֵאֲבוֹתָיו וְאֶחָיו וּבָנָיו, וְחוּץ מֵאֵלּוּ שֶׁיֵּשׁ לָהֶם שַׁיָּכוּת לַמִּצְוָה, יָכוֹל לְהַזְמִין עוֹד עֲשָׂרָה אֲנָשִׁים לְרֵעוּת. אֲבָל רַק אוֹתָן שֶׁגַּם בְּפַעַם אַחֶרֶת הָיוּ בָּאִין אֵלָיו אֶל הַמִּשְׁתֶה. וְכָל זֹאת מֻתָּר אֲפִלּוּ בְּעֶרֶב תִּשְׁעָה בְּאָב קֹדֶם חֲצוֹת הַיּוֹם, אֲבָל לֹא אַחַר כָּךְ. וְהַסְּעֻדָּה שֶׁנּוֹהֲגִין לַעֲשׂוֹת בַּלַּיְלָה שֶׁלִּפְנֵי הַמִּילָה, אֵינָהּ סְעֻדַּת מִצְוָה (עַיֵן לְקַמָּן סִימָן קסג סָעִיף ח) וַאֲסוּרִין בְּבָשָׂר וָיַיִן, אֶלָּא יֵשׁ לַעֲשׂוֹתָהּ בְּמַאַכְלֵי חָלָב. וְכוֹס שֶׁל הַבְדָּלָה בְּמוֹצָאֵי שַׁבָּת, אִם יֵשׁ תִּינוֹק שֶׁיִשְׁתֶה רֹב הַכּוֹס, נוֹתְנִין לוֹ. וְאִם לָאו, יָכוֹל הַמַּבְדִּיל בְּעַצְמוֹ לִשְׁתּוֹת.
It is the accepted custom in all Yisrael not to eat meat or drink wine during the nine days, from Rosh Chodesh until after Tishah beAv. It is even forbidden to eat food that was cooked with meat or that contains animal fat; even poultry is forbidden. However, a person, who is sensitive to dairy food, is permitted to eat poultry, and for a sick person, all restrictions are lifted. Nevertheless, if it is not too difficult for him, he should abstain from eating (any kind of meat) from the seventh of Av on. Also, some women, who have given birth, abstain from meat and wine, from the seventh of Av on, for on that day, the heathens entered the Beis Hamikdash (See Chapter 124:2 below). At a meal that is considered a mitzvah, such as a bris (circumcision), a pidyon haben (redemption of the first-born son), or the conclusion of a Talmud tractate, it is permitted to eat meat and drink wine. Aside from your parents, brothers and children, and those involved with the mitzvah, you may also invite ten other friends, but only such friends [who, if the meal would have been held] at any other time, would also have joined you. All these mitzvah meals are permitted even on erev Tishah beAv before noon, but not later than that. The festive meal, that is usually made on the night before the bris, is not considered a mitzvah meal (see 163:8 above). It is forbidden to have meat and wine [at such meals]; rather you should serve dairy food instead. Regarding the cup of wine for Havdalah on Shabbos night, if there is a child who is able to drink the greater part of the cup, it should be given to him, otherwise, the person reciting the Havdalah may drink it.