You can get the team to sign an NDA, that's how you'd make sure none of them will steal your idea, as for the tokens/coins part you can get one of the developers to do something, and use another one to review it, offer bonus for the reviewer if he finds any sketchy codes, and make sure no one knows about it so they don't make deals with each others. Also, you can (before releasing) outsource code review to another company (another NDA here).