You can fly MCO-CLT-PHL-ISP+reverse on wednesday for six segments (with Express segments --> Dash-8 and CRJ) if you feel like wasting a day (depart mco 5.37 and return 23.44).

Prices out a bit under $300 for a <$50 seg cost; or slightly more for 5 segments.

Not being familiar with your promotion I do not know requirements, so this may not be all that helpful (I assume express segments are ok, but do not feeling like confirming this).

Next week would be a bit cheaper if that is an option. This seems to be lowest cost searching same day destinations. ITH would also be somewhat inexpensive.