To answer your first question; mobile radios will perform better
than handhelds for mobile and or base use.
To answer your second question; all of the family members that use the radio must have a ham license
or be third party communicators with a licensed control operator present. If you try to use a ham repeater for frequent
personal communications the owner and other users will most likely not
However, with the above comments in mind, casual family communication between hams is usually welcome
and interesting for other hams to listen to.