‘ Then Gideon took ten men of his servants, and did as Yahweh had said to him, and so it was that, because he feared his father's household, and the men of the city, he could not do it by day, so he did it by night.'
This may mean ‘a number of his servants'. Ten is frequently used to mean ‘a number of' (e.g. Genesis 31:41). The fact that they clearly had many servants, and what follows in Judges 6:31, demonstrates the importance of Gideon's father in the town. He was a man of position and authority. Gideon no doubt chose the servants because he knew of their allegiance to Yahweh.
He ‘did as Yahweh had said to him -- by night.' His obedience was more important than the sacrifice, although both were crucial. The fact that he did it by night was not because of cowardice, but because he simply would not have been allowed to do it by day. The whole household of his father would have risen against him in fury (which demonstrates that the house of Joash, with the consent of Joash, had also strayed into Baalism), as would the townsfolk. They would immediately have put an end by force to what he was trying to do. Whereas doing it by night it could be accomplished, and the coming morning would reveal to all what had happened. Baal had been dethroned.