Q. What is the hetter (permit) for the tradition of the children stealing the afikoman? Are we not teaching them to do wrong?

A. Orchois Chaim, (473: 19) quoting Meiri, indeed maintains that this minhag is specious and unmerited. He adds that the Goyim use it to criticize the Jews, as teaching their children to steal. Piskei Teshuvos (473: n. 148) cites that Rav Chaim Soloveichik zt’l as well as the Rebbes of Lubavitch would discourage this tradition.
However, it has already become a widespread custom that children steal the afikomen and hide it in return for a prize, and it is supported by many Poskim. (Maharam Chalavah – Pesachim 9), Chok Yaakov 472: 2, Siddur Yaavetz 2:page 48: 3, Sheilas Rav p. 356: 33, Vayivorech Dovid 1: 58, Teshuvos Vehanhogos 3: 141, et. al.).The best known reasons for hiding and stealing the afikomen is to arouse the children’s curiosity. (Likutei Maharich 3:p. 519).
According to the opinion of Horav Elyashiv zt”l (quoted in Halacha Shel Pesach 2: p. 301: fn.. 72), this is an acceptable and beautiful tradition. The reason given is as the Talmud (Pesachim 30) teaches that we grab matzos on the night of Pesach so that the children do not fall asleep.
The interesting following reason is offered for the tradition of “stealing” the afikomen. We know that the dogs did not bark on the night of Yetzias Mitrzayim. The Talmud (Pesachim 113a), teaches that people are prompt to steal when dogs do not bark, since the dogs offer then not a deterrent. So to remember that miracle the custom is to steal the afikomen (Minhag Yisroel Torah 2: p. 291:16, Moadim L’simcha 5: p. 345: fn. 12).
Theft is normally prohibited, even if it is done for a joke, in order not to accustom oneself to steal. (Rambam H. Geneiva 1: 2, Shulchan Aruch C.M. 348: 1).
It can be argued that encouraging children to steal the afikomen is bad chinuch. However, if the thief is a member of the household, then there may be no concern since the owner of the house does not mind at all (Halichos Shlomo – Moadim p.260: fn. 219, quoting the custom of Harav Shlomo Zalman Aurbach zt”l).
Piskei Teshuvos (473: 26) quotes that it is not correct to call this minhag “stealing” the Afikomen, rather one should name it “grasping” or similar,

Rabbi A. Bartfeld as revised by Horav Shlomo Miller Shlit”a