8:1 This psalm begins and ends with the same expression of wonder as David reflected on the splendor and magnificence of the Lord. He addressed God as LORD (Yahweh, the covenant keeping God of Israel) our Lord (Adonai, the sovereign over all His creation including His people). In the second line David meant God's revealed character ("name") is high above all creation; He is much greater than anything He has made. The third line expresses a parallel thought. Not only is God above the heavens, but His splendor exceeds that of the heavens.
8:2 In addition to the earth and the heavens, even the weakest human beings bring praise to their Creator. David's point was that even small children acknowledge and honor God whereas older, more sophisticated adults often deny Him (cf. Matt. 21:16). God has chosen to use the weak things of this world to correct the strong (cf. 1 Cor. 1:27). Supposedly the young child of an atheist couple once asked his parents, "Do you think God knows we don't believe in Him?"