Prima Pars: Is God taken by surprise?
I love this question! When I see these depictions of the Divine, I immediately engage in source criticism. For me, it is noteworthy that both verses you cite are from the J source. Contrast the two passages in Genesis which relate the Divine's decision to flood the world:
Genesis 6:5-7, J source
5 When the LORD saw how great the wickedness of human beings was on earth, and how every desire that their heart conceived was always nothing but evil, 6 the LORD regretted making human beings on the earth, and his heart was grieved. 7 So the LORD said: I will wipe out from the earth the human beings I have created, and not only the human beings, but also the animals and the crawling things and the birds of the air, for I regret that I made them.
Genesis 6:11-13, P source
11 The earth was corrupt in the view of God and the earth was full of lawlessness. 12 When God saw how corrupt the earth had become, since all mortals had corrupted their ways on earth, 13 God said to Noah: I see that the end of all mortals has come, for the earth is full of lawlessness because of them. So I am going to destroy them with the earth.
Notice how there is no depiction of the Divine 'repenting' or 'grieving in his heart' in this P source account. Anthropomorphism characterizes the J source, attributing uniquely human qualities to non-human entities. A few instances of this in the J source Creation account include: the speaking serpent, the Divine forming (the verb 'יצר' here is also used for a potter molding clay with his hands) the human from the earth, the Divine blowing the breath of life into the human's nostrils, the Divine walking around in the garden, etc.
It must be recalled that anthropomorphism is a literary device, nothing more and nothing less. It is not an attempt to define the Divine's essence. Indeed, if the use of anthropomorphism by an inspired writer were to be regarded as a serious attempt to define the essence of whatever entity it was describing in the narrative, we would also be discussing if serpents were really capable of speech!
So the question for me is not: Can the Divine really be surprised? The question becomes: What is this surprise meant to communicate? For me, the surprise communicates an almost violent rupture in the relationship between the Divine and humanity. Whereas before the Divine was intimately conscious of his Creation, the exercise of human agency in violation of the Divine's counsel has broken that intimacy to the point where God can no longer even find the first couple!
8 When they heard the sound of the LORD God walking about in the garden at the breezy time of the day, the man and his wife hid themselves from the LORD God among the trees of the garden. 9 The LORD God then called to the man and asked him: Where are you?
Immediately after they eat of the forbidden fruit and sew their fig leaves, the Divine anthropomorphically comes down from the Heavens and walks on the earth in order to find the human couple. For me, this text communicates a simple, yet poignant message: when you sin, when you feel cut off from God, when you turn away from the Divine, he will come to you speedily, to seek after you if you but respond to his call. God does not abandon you.
Secunda Pars: If God is not genuinely surprised, then did the Divine orchestrate the fall of humanity?
I apologize for not addressing your second question! Especially because I think it is such a crucially important question. However, you will have to indulge me in my response since I believe that in order to address it properly I will have to go beyond the scope of the text. This may well be something with which many people will disagree, but I think your question goes to the root of the difference between the ancient Israelite mindset and the Hellenistic mindset. I will quote Diogenes Allen, who expressed this distinction far better than I can:
In contrast to Aristotle, the claims made by Genesis and the rest of the Scriptures do not spring from a desire to discover the principles of nature's operation, nor even to account for the existence of the universe. Belief in a Creator is not affirmed by the ancient Israelites because they desire to explain the world's existence and order. [The world's] existence and order do not form the grounds for their belief in God. On the contrary, they believed in God because they believed God's self-revelation... Their belief in the divine is a response to God's initiative rather than the result of their investigations of nature's order and origin; cf. Allen, Diogenes, and Eric O. Springsted, Philosophy for Understanding Theology (Louisville, KY: Westminster John Knox Press, 2007).
The Israelites noted that the human condition was characterized by discord, and they properly understood this as a rebellion against Divine wisdom. However, the ancient Israelites were also appropriately repelled by the prevailing Babylonian religious dogma, which understood humankind as having no inherent worth or dignity [cf. Nahum M. Sarna, Understanding Genesis: The World of the Bible in the Light of History (New York, NY: Schocken Books, 1966)]. Both of these convictions are prominently displayed in the powerful Creation narratives of Genesis: humankind is created in the very image of God, with God's own breath/spirit, rather than from the blood of a defeated enemy (Marduk's creation of humans as slaves, from the blood of Kingu).
So, I believe your question has a great deal of merit, but I do not think the texts were written in order to tackle that particular problem.
If I were to grossly oversimplify, a possible solution to your question may involve how one understands human agency, whether libertarian or determinist. If you believe that human agency is free, then it is humans who choose rebellion against the Divine. If you believe that human agency is determined, then it was the Divine who created the world in such a way that the causes would ultimately lead to human rebellion against the Divine. Again, this goes beyond the text of Scripture, which I am loathe to do in a Biblical Hermeneutics message board.