I'm sorry you're having such a hard time. But I would hate for you to leave that place and regret everything that happened. Definitely try everything Vivianne mentioned.
Also, there has to be some sort of shop that has handheld fans. Some even come with spray bottles to spray and fan yourself at the same time. Fill that puppy up with ice water. Is there a pool? I'd be in it every minute if I were there as I am extremely sensitive to the heat as well.
I'm sure you're family is willing to help in anyway just to see you have a good time. Open up to them and see what they suggest. They're there so they may have ideas of places that are cool and then everyone can have a good time together.
October 29, 2009 - Dx with RRMS
June 22, 2010 - Dx's changed to Devic's (NMO)
January 4, 2011 - Dx w/Syringomyelia T4-T9, Migraines, and Possible MS (again - long story)