I am from eastern Canada and quite frankly I do not enjoy the heat at all. The hottest we typically get during the summer months is 26 degrees C (or 80 degrees F). I had been to Fl several times in November and December and loved the temperatures at that time of year. My first trip down to Florida in August, I was very concerned about coping with Florida's summer temperatures but DH is a teacher, and between my job and his, we can only travel during the summer months. I am now planning my 6th August trip to Florida and I have no worries at all.
You do get used to the heat although it can be draining and make you and your family irritable. We have coped by
1. being most active early in the day and late in the evening.
2. In the hottest part of the day, we try to take advantage of air conditioned attractions where possible or go back to the resort and spend the afternoon in the pool.
3. Take your lunch at a sitdown restaurant in the park with air conditioning. It helps to take that break out of the sun.
4. Hydrate, hydrate, hydrate! You become dehydrated quickly without even realizing it. We bring a water bottle and just keep refilling it at water fountains otherwise it gets very expensive.
5. The misting fans are surprisingly refreshing and can take the edge off the heat.
6. Wear very lightweight clothes. I have found that keeping my shoulders and back open to the air allows any breeze help to cool me down but you'll have to make sure to use lots of sunblock. Avoid collared shirts as they make you surprisingly warm to have material on the back of your neck.
The main thing is to remember to have fun and make allowances for the heat if you are not used to the summer temperatures that Florida produces. No worries though, you will have a wonderful trip!