This question is directly answer in :סוכה מו...
"ואמר רב זירא לא לימא איניש לינוקא דיהיבנא לך מידי ולא יהיב ליא משום דאתי לאגמוריה שיקרא שנא' למדו לשונם דבר שקר"
“And Rav Zeirah says: A man should not say to child that I will give you something and then not give it to him, as it will teach the child to lie, as it says; ‘They taught their tongues to speak lies’ (Yirmiya 9:4).”
HoRav Yaakov Ettlinger זצ״ל, in his famed opus the עורך לנר, asks a fundamental question on our גמרא. The גמרא reads that by telling a child you will give him something and then failing to do so, this teaches him to lie. But in reality it is the father who is doing the lying. So why does the גמרא not say that the father is transgressing the עשה of מדבר שקר תרחק? The עורך לנר answers that in our case the father is not in fact lying. The גמרא was talking in the context of taking לולבים. It instructs that a person should not give his לולב to his child on the first day of יום טוב because whilst the child has the power to be מקנה (acquire) the לולב he does not have the Halachic capacity to give it back. Should this happen, the father will be without his ארבע מינים for the rest of יום טוב. Says the עורך לנר; a father can still give the לולב to the child not as a מתנה, but temporarily, for חינוך purposes. The father is consequently not lying as his intention is not to fully hand over the לולב but rather to show his child what to do with it. However, when the child grows up and learns the הלכות he will see that he never really fulfilled the מצוה since he did not actually own the לולב. The עורך לנר writes: “ועל ידי זה מלמדו לדבר שקר במרמה” – “And through this he will learn to speak falsehood in deceit”. This means that whilst his father had good intentions, it nevertheless created a situation whereby the child feels deceived by his trusted teacher – his father. This being the case, he might come to learn that lying is justified, and this is why the גמרא had to specifically state that it will teach the child falsehood.
So taking this within the context of your question it is perhaps best practise to acquire at least a kosher set (doesn't have to be מהדרין מן המדרין) so when he becomes more familiar with the halochos he will be happy that it was done כדת וכדין.