All those are great suggestions! I'd throw out any rules about beverages if you have any (like I normally don't give juice boxes or flavored milk except once in a blue moon, but if I was worried my kid wouldn't drink anything I'd relax the rule for a couple days during a real heat wave.)
Squeeze pops, popsicles, sherbet, melon, anything! Good luck. Oh, if you have a Sonic in town, they have the best ice and you can buy it by the bag! My daughter can't resist just crunching the little ice chips.