Returning to Egypt?

YHWH says, "Let my people go, that they may serve me in the wilderness." At one point Moses explains this involves traveling three days into the wilderness to sacrifice. The implication, however, is that they will return to Egypt! How can that be?

If the goal was to leave Egypt behind entirely and travel to the Promised Land, then why did YHWH only ask for his people for a few days of sacrificing/feasting/worshipping? Why didn't he ask for more? He could have told Pharaoh, "Let my people go, for they are my slaves and not yours, and I will utterly remove them from your grasp."

Is God just playing around with Pharaoh, knowing that he won't grant even the smallest request and taking it as an opportunity to level his nation? In any case, why don't the People of Israel return after doing their sacrificing and worshipping in the wilderness? Is it because Pharaoh and his firstborn son are dead? If Pharaoh hadn't died in the Red Sea, would Israel have returned to Egypt and continued serving him? Or is Pharaoh's death inconsequential, with Israel continuing on to Canaan regardless?