Plan for the rain, you're planning your trip during our wonderful Hurricane/rainey season. However, all that means is a couple of .87 ponchos and a good spirit. Seriously, you aren't made out of sugar, you won't melt. I personally LOVE to see people run for cover during the rain ... that's when we head off for a good couple of rides, with no waits. The only time I don't recommend this is when someone's made Mother Nature angry and there is lightning in the air.
Yes, it's HOT. Hello, it's Florida. It's almost always hot. We're in the 50's right now for lows, and we're all crying about it .... hahaha ... go figure. Does the fact that it's HOT mean anything .. eh, cranky kids. Your guys are old enough to know a little better ... you just have to work with them mom. Sure, the eight year old might think you're nuts when you suggest leaving the park to go back to the room and take a rest *don't drop the nap word* ... however, an hour in a cool hotel room, maybe a swim ... you're ready to go. We usually camp at Wilderness, but my daughter is two so the nap word is crucial .... my sister is nine and doesn't like hanging out with the baby .. but if she's getting cranky, I make her lay in her bunk with a good book or her DS to rest. Parents need rest too, you don't want to be the parent that yells "Do you know how much I paid for this trip?!?!?!" I found something that works though instead ... at the end of the Pirate and Princess party, it was 12:30am ... my sister was DONE. She decided to throw one heck of a fit where I calmly explained to her "Walt wrote a rule book, there's no whining at Disney, do we need to go look at it?" "BUT, I waannnaa ride another riiiide, SIIISSSSSYYY" "There's NO WHINING AT DISNEY, we're going home!" Good thing we really were going home ... haha ... but yeah, cranky parent ... bad situation.
I live down here ... and we don't usually go in June. No offense, but it's too darn hot ... but we can go for weekend trips anytime ... we can be picky... That'll change when Julie's older, but right now we usually skip over the summer b/c we have that option. I say enjoy it ... get a nice tan, play in the rain *hopefully just enough* and meet some new friends while in line for some rides.