You'll have to put a condition around it in the USERCP_SHELL template:
HTML Code:
<if condition="is_member_of($bbuserinfo, 5, 6, 7)"><tr><td class="$navclass[event_reminders]" nowrap="nowrap"><a class="smallfont" href="calendar.php?$session[sessionurl]do=viewreminder">$vbphrase[event_reminders]</a></td></tr></if>
Usergroup ids 5,6,and 7 are the mods and admin. Change those as you see fit.