Okay, take a deep breath...Calm...
Let's turn this around...Think of all the space you'll have in your suitcase because you didn't need to pack jeans and sweatshirts!And that space can be filled up with souveniers!
Thousands, maybe millions, visit the world at this time of year and have a wonderful time. Whether you have a good vacation or a bad vacation is entirely up to you. WDW is ALWAYS magical, no matter what the weather, temp., or month.
You do need to visit the parks early. If you are staying onsite, take advantage of EMHs. When it starts getting too hot or the kids start to look a bit wilted--GET OUT! Go back to your hotel for a swim/lunch/rest and don't go back to the parks until all of you are revived. This is so important.
I know you may feel like, "hey, I'm wasting my day lounging at the hotel, I should be in the parks making the most of my money."
You can't think this way! If you tour the parks commando-style in the heat, YOU will ruin your vacation. Your kids will literally melt-down. I've seen it happen. I've seen kids laying on the ground in the parks, crying. The moms are sweating and look exhausted and frazzeled. They are definately not having fun. I want to go over and say to them, "Maybe you guys need a little park break."
Of course I don't. I just look over at my 5 kids who are refreshed and excited and having a great time and I know that I made my vacation magical by using common sense and mother's intuition.
Have a wonderful vacation just use common sense. All those people who are poo-pooing your plans are just jealous that they aren't going anytime soon!