I fully understand. Thanks for the amazing job so far!

if it may usefull, as a workaround, you may create as many subdomains as necessary for each family (familly1.yourdomain.com, familly2.yourdomain.com,...)
then install as many zenphoto as necessary on these subdomains.
on each domain, you have only users of a familly.
and then protect each zenphoto with a specific password.
of course, with that, there is no shared albums or news, and you have to adminstrate few zenphoto instance...

Thanks for your kind help Vincent! That is indeed another good option. However, I think I am going to stick with the current solution and wait for the change. I really enjoy the current set-up.