Only members of the list can send an email to the list - since the list names are tied to the sender's address you don't need to worry about uniqueness (ie. my family@fiesta.cc is different than your family@fiesta.cc)
*btw, I would not use a ".cc" domain for the project, since it is mostly used by malware stuff lately :/
Also, they wanted like $1M for fiesta.com or something :P
Edit: On WHOIS, I see you've already had this idea...