"My son will be 6 years old. Is swimming with the Dolphins at Discovery Cove a good Idea?"
If he is a good swimmer, yes. I had a wonderful time there last spring, and the majority of your day will be spent snorkeling, laying out, checking out the bird aviary, and eating some good food. The actual dolphin swim only lasts about 1/2 hour, but it is quite remarkable. The majority of it takes place in shallow water, and if he wants to, he can "ride" the dolphin back to shore, but only if he can tread water for a little whileand is not afraid of deep water.
Also, if you visit Discovery Cove, you are given a week's pass to Sea World. The parks are right next door to each other, and it makes a nice addition to your vacation.
"How far in advance do you have to book into the Kennedy Space center to see a launch. There will be one on 28/10? Is it worth the extra trip? What do we need to know and what do we need to do…"
As far as shuttle launches go, you can see them from miles and miles away. I drove over there to see one YEARS ago, and it was a blast seeing people from all over the world and seeing license plates from all across the USA. You can just drive east on Route 528 as far as you can go and once the traffic starts getting bad, just pull off to the side of the road and watch the launch. But be prepared for a MAJOR traffic jam on the ride home.
To make the launch enjoayble and tolerable, bring a cooler with snacks. The Space Center is only an hour's drive east of Orlando. If you want to make a day of it, you could spend it at the Space Center checking out the exhibits. I don't know if they have a shuttle or special viewing area on launch days, but it would be worth inquiring about.
Hope this helps you! The weather that time of year is PERFECT, and the crowds seem to be non-existent, except for the special events at Disney and Universal. If you can, try to do either one of these on an off night. That is, visit the parks during a week day and EARLY in the Halloween season. If you go to HHN on a weekend, be prepared for lots of people and long lines.
Also, as an Orlando native, may I suggest some better places to eat rather than the chain restaurants on International Drive. For good food and good pricesm check out the Orlando Ale House. There is one in Lake Buena Vista near Downtown Disney.
On Disney property, my favorite buffet restaurants are Boma at Animal Kingdom Lodge, and Ohana at the Polynesian. Both have great food, and Ohana really makes an effort to entertain the kids there.