Take Aaron and his sons with him...
Leviticus 8:2

God never asked Aaron or his sons if they wanted to be priests for the people of Israel. Sometimes there's a role to fill and God will take any qualified person who is willing. Sometimes there's a role to play and only one person will do. God called Moses to lead the people, Pharaoh to be his foil, and Aaron to lead the people's worship. None of them had any real say in the matter.