co-opt someone into something
to convince someone of a differing view to adopt one's position or philosophy. They tried to co-opt the students into rioting. There is no point in trying to co-opt them into it. They are too clever.
opt for something
to choose a particular option. I opted for the orange one. I opt for not going out at all.
opt in favor of someone or something
to choose a particular person; to choose a particular thing. Do you think she will opt in favor of this one or that? We will opt in favor of David.
opt in(to something)
to choose to join in. She opted into our plans. She opted in almost immediately.
opt out (of something)
to choose not to be in something. If you do that, I'm going to have to opt out of the club. Then go ahead and opt out.