how well do mature indoor cats tolerate heat?

hello! I am going away for a week and a friend of mine will be stopping in to check on my cats (Simba and Nayla. Should she stop in every day? Every other day?

Friend should come twice a day to feed the cats & check on them and clean out the litter box. Make sure the water is changed regularly.
   
Leave the air conditioning on at no warmer than 75 degrees. Cats can't sweat, they can easily succumb to heatstroke.
   
Cat-proof the house, cut them off from anything they're likely to get into trouble with. You could confine them to one room if you think it would be safer.
   
Give your vet a signed letter authorizing your friend to get the cat vet care in an emergency. The vet needs authorization. Give your friend a copy of the letter.
   
Check in with your friend at least once during the time you're gone.