Moses sent his wife and kids away?

Exodus 18:1 says, “When Jethro, the priest of Midian, Moses' father in law, heard of all that God had done for Moses, and for Israel his people, and that the LORD had brought Israel out of Egypt;

18:2 Then Jethro, Moses' father in law, took Zipporah, Moses' wife, after he had sent her back,

18:3 And her two sons; of which the name of the one was Gershom; for he said, I have been an alien in a strange land:”  First I must ask how Moses’ father-in-law had heard of what god had done?  The Israelites were wandering in the wild and the Egyptian men were killed.  But my real question is in the Middle of the exodus Moses sent his wife and kids back to his father-in-law?  I guess they weren’t lost in the wilderness.