MAC Hotspot Exception

Is there someplace I can enter in a MAC address so the hotspot server automatically lets it through?

yes, in hotspot ip bindings

ip hotspot ip-binding print
Flags: X - disabled, P - bypassed, B - blocked
 #   MAC-ADDRESS       ADDRESS                         TO-ADDRESS      SERVER
 0                     192.168.100.0/24

place this mac addr on the #1 place

/ip hotspot ip-binding add mac-address=00:00:00:00:00:00 place-before=0 type=bypassed

Karma for you!

Thanks.