Yaakov declined Esav's offer because it would have inevitably meant quickening his pace, which would have resulted in the death of his animals. Why did he add, "until I arrive... in Se'ir"?
Rashi and Ramban: He did so in order to put off Esav, since in fact, he was only going as far as Sukos. 1 So should Esav wait for him to arrive in Se'ir 2 in order to kill him, he would have a long wait. 3
Avodah Zarah 28b: We learn from here that if a Nochri who wishes to accompany you on a journey, asks you where you are going, you should state a destination that is beyond where you really intend to go; so that, in the event that the Nochri plans to kill you, you will be able to arrive at your destination before the Nochri has a chance to carry out his plan.
Malbim: Yaakov promised to go to Se'ir; Esav retracted and went to his father's house first (36:6). Yaakov saw him there, so he did not need to go to Se'ir, even after Esav went there after Yitzchak died.
Ha'amek Davar: Esav wanted to honor Yaakov soon in Se'ir. Yaakov said, I cannot receive honor as long as I am distracted with the flock and raising children. Later I will go alone, and my heart will be open for [honor].
According to the Ramban, his itinerary led him close to Se'ir, which he had the option of passing through, and Esav, assuming that he intended to do so, offered to honor him by accompanying him until he arrived home.
As a matter of fact, he would eventually arrive in Se'ir - in the days of Mashi'ach, as the Navi writes in Ovadyah (1:21). See Ba'al ha'Turim and Ramban.
What is meant by, "Esnahalah l'Iti l'Regel ha'Melachah... ul'Regel ha'Yeladim"?
Malbim: I will lead the weak animals. Sometimes the pace depends on the need of the flock to graze, or [to go to shade] in the afternoon. Sometimes one must go slowly due to the young animals, at the times of eating and sleeping.
