Multiple admin accounts

Setting up multiple admin accounts in WHM is easy, simply create a reseller user then grant them root access privileges via the Reseller Center (or privileges screen when you grant them reseller access).

Regarding logs, I'd be surprised if there wasn't a log to log activity in WHM. Off-hand I don't recall what that log would be.

 

Here's a list of log files the folks over A Small Orange put together for their VPS customers. It's a fairly exhaustive list of the log files generated on a cPanel/WHM system

Apache
/usr/local/apache/logs/access_log
/usr/local/apache/logs/error_log
/usr/local/apache/domlogs/example.com

MySQL
/var/lib/mysql/hostname.err

Exim
/var/log/exim_mainlog
/var/log/exim_paniclog
/var/log/exim_rejectlog

Courier-IMAP
/var/log/maillog

cPanel
/usr/local/cpanel/logs/error_log
/usr/local/cpanel/logs/access_log
/usr/local/cpanel/logs/login_log
/usr/local/cpanel/logs/stats_log

Pure-FTP
/var/log/messages
/var/log/xferlog (symlinked to /usr/local/apache/domlogs/ftpxferlog)

System (cron, syslog, named, etc)
/var/log/messages
/var/log/boot.log
/var/log/cron
/var/log/dmesg

Security (ssh, ModSecurity, etc)
/var/log/secure
/usr/local/apache/logs/audit_log
/var/log/messages