I hate the heat and don't do well with it, funny since I'm a native Texan. Anyway last year we were at DLR during the heat wave and oh, man was I complaining every day!!! Drink lots of water, alternate with the nice cool drinks like the lemonade icees or the apple juice ones

Avoid caffeinated beverages. Yes to taking a break in the pool during the hottest part of the day, which I felt was more like between noon-3pm. When the sun just starts to go down the air begins to cool so we found that 4-5pm felt better than noon (this is different from TX where 5pm is considered the hottest part of the day. Breeze tends to pick up in the late afternoon too which helps a ton. Be sure to apply lots of sunscreen at the start of the day.
You can't necessarily count on getting soaked on Grizzly...only one of our party of 8 this year got wet enough to describe as "soaked". But if you want to ride, FP for sure!
We were not opposed to filling a bottle of water and then just pouring it over our heads

That helped the kids out a ton. I prefer quick-drying sport sandals rather than tennis shoes/socks for this reason - you can dump water on yourself to cool off and still walk around in comfort. Same with clothing, pick quicker-drying fabrics.
Sun hats!!! We all have dark hair and it's amazing how much cooler you feel with a good wide-brimmed sunhat. We got ours from Costco (as did 50% of the others in the park, LOL, so be careful when watching your kids - don't go by their hat color!) but they worked GREAT. You can even wet the hats, wring them out, and wear them. Aaaahhhhhhh, feels so good.
We personally found the mister fans to just be a pain to carry around.