It does not matter a lot if the minisite is part of the domain, subdomain or separate domain. It is the same work with content obviously.
Domain, subdomain or separate domain have advantages and disadvantages for SEO (parent domain in case 1 and partially 2 can pass trustrank; case 3 can better target keywords as EMD or PMD), which should be considered. The last thing visitor cares about is if he is on third.domain.com or domain.com/third.
If you talk to God, you are praying; If God talks to you, you have schizophrenia.