I think even just offering @namekin.com as an option, and allowing people to start mailing lists for their families would be awesome as well (of course, offering this for the domain option works too). Since some last names are way too common, it could even make sense to figure out a good list of most common domains to buy ahead of time and offer to use them to families. Of course you gotta make sure they understand other families with the same last name could be using those domains.

You could offer a single @namekin email as a sample of the whole service as well, which might go a long way and get you more feedback.