How much $ to turn thermostat up for a tropical theme party?

So this weekend we're having a tropical theme party where everyone wears swimsuits and stuff, so i was planning on turning the thermostat up to get it nice and hot. So my questions are,



1. What would be a good comfortable temperature?

2. How long before the party should I set it?

3. How much extra will is cost (heating with gas, and about a 2000 sq ft house?How much $ to turn thermostat up for a tropical theme party?75-78 1 hour it wont cost much for just a few hours maybe $20 or so nice theme for this time of year, so have fun and cowabunga dude!