I wrote something like that for another customer. The query below should get you started.
select '' as Fullname --This is your additional option. A blank value in this case, but could be 'N/A'
select distinct U.FullName
from Groups G, Users U, GroupMembers GM
where G.Groupname = '' -- Enter group name here between the single quotes.
and G.GroupID = GM.GroupID
and U.UserID = GM.UserID
and U.Enabled = 1
--For mulitple groups, add another union command here and then re-use the group member syntax from above and search for a different group name.
order by Fullname
Derek M. Lawson