Chinuch Horaah of the Day:
One needs to make efforts that Lag Ba’omer, the Rashbi’s day of simchah, will be yom simchaseinu, the day of our rejoicing. This applies to all of Bnei Yisrael, wherever they are (in chutz la’Aretz, and how much more so in Eretz Yisrael) through organizing celebrations and parades and the like, which involve men and women (separately, with the ultimate tznius of course) and children.
Especially regarding the children, in accordance with minhag Yisrael (which is Torah) going back many generations, on Lag Ba’omer the teaching of children is reduced for half or a third of a day, and people go out to (seemingly) celebrate with children in permissible matters (inyanei reshus).
However, since it is tinokos shel beis rabban that we are speaking of (who are getting a proper education), this is done sincerely as a minhag Yisrael Torah hi, to the point that this adds to their desire to learn Torah (after Lag Ba’omer), and as a preparation beforehand, in their knowing that Rashbi’s life and essence was all about Toraso Omanaso (his Torah was his main occupation).
(Hisvaaduyos 5748, vol. 3, p. 269)