What will be burned?
What is the law of "Oso v'Es Kol Asher Lo"?
Rashi: It is like it says below. The sinner and animals are stoned. The note Zakef on "ba'Esh" proves that it is separated from "Oso" (i.e. he is not burned). Only what is proper to be burned, it is burned, like it says below (verse 25). The verse here did not say the law of him and his possessions; it is given below.
Radak: Because he transgressed the Cherem, all his property becomes Cherem. His minor children are included in his property. His adult children are liable for seeing and being silent. [Achan] did not have a wife. If he had a wife, she did not know, for he hid it from her
Why does it say "Ki Avar Es Bris Hashem v'Chi Asah Nevalah b'Yisrael"?
Malbim: "Avar" is against Hashem; he transgressed His Bris. "Asah Nevalah b'Yisrael"