According to the passage (Mt chap 2) the Magi unexpectedly provoke Hero who ends up causing Joseph & company to flee to Egypt. Which then results in their return from Egypt. All of which Matthew sees as a fulfillment of a divine pattern destined to be fulfilled in Jesus. ("Out of Egypt I called my son.") Even the mayhem caused by Herod is seen by Matthew as having been foretold. (The quote in Mt 2:18 is from Jeremiah in 38:15 LXX. & 31:15)
The Magi also unexpectedly fund the whole adventure (a la the queen of Sheba, who sets up a pattern of faith shown by gentiles).
To say that the Magi were used by God, well, in a sense they were used, just like Balaam was used in the book of Numbers. In Numbers chapters 22-25 Balaam was 'used' by God only after he began his trip for selfish purposes. Matthew chapter 2 only shows the Magi being "used" by God after their having been summoned by Herod. In the account, they did not go straight to Herod. Nor does Matthew say that the star led them to Herod. Rather, Herod hears of the commotion that the Magi unintentionally caused and then summoned them to find out about it. (Mt 2:3, 7) Herod then shows his intention to kill the child and God intervenes. I don't see anything unexpected in that.
As for the Magi going to Jerusalem first, well, that would be the expected place to go if they were searching for "the king of the Jews," would it not? So, there was nothing sinister in them going there in the first place. They went to the place one would naturally expect to find a "king of the Jews."
The whole affair in Matthew chapter 2 is also recognized by many commentaries as a pattern in the whole book of Matthew where Gentiles show unexpected faith, but Jews (in general) show a surprising lack of it. So part of Mathew's purpose of including the account in chapter 2 is a larger theme woven into the whole book.
It did not necessarily have to be God that "used" them initially. In the account it was only after Herod summoned them that God is spoken of as intervening to protect them (Joseph and family, that is). That would naturally be expected if Jesus was actually God's Son and God had a further purpose for him on earth, would it not?
Anyways, that is my take on it. The WT take on the account assumes that the Magi were being used by Satan from the get go, and that the Magi went straight to Herod and that the star led them there. None of which the account in Matthew actually says. My take attempts to avoid all those false assumptions.
But, as they say, "Your mileage may vary."