Usually, when we reference the relationship of Hashem and the Jewish people, we use the example of the love of a father to a little child, since such a love is essentially pure- and not yet dependent upon additional external virtues. Why then when Moshe Rabbeinu approaches Pharaoh does he reference the Jewish people using the term of an older child? The answer is, that although when we are older and develop our minds and hearts and start doing Torah and mitzvahs, Hashem also loves us for everything we accomplished, Our achievements only enhance the pure essential love and commitment of the little child - which is the basis of our relationship with Hashem. We know that Hashem wants us to utilize all our capabilities to serve Him, and therefore, even though He loves us now, He also does for what we accomplished. That doesn’t diminish the initial love of the little child. Therefore, when referencing the relationship of a Hashem to the Jewish people we utilize the terminology of the love to a little child, but when we’re talking about who the Jewish people are and what they’re capable of accomplishing, we utilize the terminology of an accomplished older child, that still maintains the special relationship, the innocence and the connection of a father to his little child.

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לקו״ש כא-ג