One thing I plan on doing is re-applying mid-day. I'm bringing individual make-up remover cloths to use in the bathrooms, then I'm just going to re-apply sometime in the afternoon. It only takes me about 5-7 minutes to do my make-up (foundation, concealer, powder, mascera, eyeliner, natural-colored lipstick), so I think this is the best option for me.
Also, Revlon waterproof mascera will NEVER wash off in water(unless your rub on it, of course). I've gone swimming with it and it looked as good as new when I was done. I've also gone into the ocean before with Revlon waterproof eyeliner and it BARELY smudged. It was amazing. I highly reccommend their eye products!
And Almay's liquid foundation, consealer, and pressed powder work pretty well during heat. Just don't cake it on, dab the sweat off, and use those oil sheets rather than caking on powder.