Siman 596
Presented here for study, not as a practical ruling. The Shulchan Aruch rules by Sephardi custom, the Rema's glosses by Ashkenazi custom, and the Kitzur follows Ashkenazi custom. For a practical question, ask your rabbi.
א לְאַחַר הַתְּפִלָּה מְרִיעִים תְּרוּעָה גְּדוֹלָה בְּלֹא תְּקִיעָה. הַגָּה: וְיֵשׁ מְקוֹמוֹת נוֹהֲגִין לַחֲזֹר וְלִתְקֹעַ ל' קוֹלוֹת (מִנְהָגִים יְשָׁנִים); וּלְאַחַר שֶׁיָּצְאוּ בָּזֶה, שׁוּב אֵין לִתְקֹעַ עוֹד בְּחִנָּם; אֲבָל קָטָן, אֲפִלּוּ הִגִּיעַ לְחִנּוּךְ, מֻתָּר לוֹמַר לוֹ שֶׁיִּתְקַע (הַמַּגִּיד פ"ב מֵהִלְכוֹת שׁוֹפָר), וּמֻתָּר לוֹ לִתְקֹעַ כָּל הַיּוֹם (אוֹר זָרוּעַ דְּרֹאשׁ הַשָּׁנָה).
1 After the (Musaf) Prayer, we trumpet a big teruah blast without a tekiah blast. Rema: There are places that we are accustomed to go back (after the Musaf Prayer) and blast 30 sounds (Minhagim Yishaynim) and after one fulfills these, further there is not to blow more for no reason. But a minor, even one who has reached the Halachic age of maturity, it is allowed to say to him that he should blow the shofar (The Maggid Chapter 2 from the Laws of Shofar). And it is permitted (for a minor) to blow shofar all day (Or Zarua of Rosh HaShana).