Right, breathe, I completely agree with pp easywdw.com by Josh has maps that show you which things you might want to visit first and things will get busy.
Ignore the hurricane season crap, WDW is inland and yes, there is a rain storm (think torrential) pretty much every afternoon in August but you are going when the US schools are back and a lot of Brits go. The only reason I'm going earlier is because of DS1 getting his GCSE results.
The rain, you can see it coming. It is not a surprise. You can see the clouds moving in. We got really good at predicting when it would rain.
Disney resorts such as CB are all served by a wonderful bus service, air conditioned. You leave your room and walk to the bus stop, the buses have their destinations on the front and you get on the one you want. Simple. It will drop you at the park bus station, just follow everyone who gets off as they are all heading in the same direction as you.
Disney has 4 theme parks, Magic Kingdom (probably the most well known with rides, shows, and the most incredible fireworks every night) Animal Kingdom (self explanatory) but with rides and shows, Hollywood Studios (rides, shows and fireworks) and EPCOT (again with those rides, shows and fireworks) and there are two massive water parks. All this is included in your ticket price. You will be given a "magic band" (wrist band like a watch) this is your park ticket and your hotel room key. You can set a pin and charge food, purchases back to the room.
Videos wise, I highly recommend Tim Tracker and on Youtube. Seeya are a married couple, I have linked you to a playlist of theirs, you will see them land in Orlando airport, catch the Magic Express, check into their room and catch a bus to a park.
My youngest son was only 7 when we first went and this was helpful for him to visualise it all. Worth a binge watch.
The Dibb is a great UK website full of trip reports, photos, and a forum to ask questions. I have been on there for years. No question is too stupid, yes it probably has been asked before and many times but it is a very friendly place and we are all there to share our love of Disney.
How old are your children and what do they like Disney wise. Start with working out what they will want.
Universal is much smaller, you are booked into one of the most expensive hotels on property 
and you will get front of the line passes (express pass) meaning you'll spend less time queuing, we stay at Royal Pacific resort also on property.
It does seem daunting, but lots of us have been several times and we are here to help.