1. If you want to make an ADR for Breakfast at MK, do it super early. If MK opens at 8, you can start making ADRs at 7:05. If it opens at 9, you can make them at 8:05. However, if it opens at 9, but Extra Magic Hours start at 8, you can still only make reservations at 8:05. If you do this, you can get in the park earlier, and if you finish eating before the park is technically open, you can still go out and do things like take good pictures in front of the castle with nobody behind you, etc.
I'm not sure they do early ADRs in the other parks, but I know you can at Magic Kingdom.
2. If you want a spot for a parade or a firework show, especially a parade, get there and claim your spot 45 minutes to an hour early. I cannot tell you how ANNOYING it is, when I've been sitting somewhere for an hour with a great spot waiting patiently, and in the last 5 minutes a family comes and completely blocks my view. Me being a solo visitor, it happens all the time. I just get surrounded like I'm not even there. I once had a family get so close to me they were pushing into my back while I was sitting. I usually try to sit near a trash can for a parade so at least they can't do that on one side of me. But it is seriously rude when that happens, one of my biggest pet peeves in the parks.
Also, if you want to put your child on your shoulders, please be aware of your surroundings. I understand that the shorter child should be able to see, but make sure you aren't completely blocking someone else's view behind you. If I knew a child couldn't see , I would GLADLY offer for them to come stand in front of me because I know I could see over them no problem, but for a dad who is already at least a foot taller than me to come stand directly in front of me, to also have someone sitting on his shoulders to block the view even more, it's obnoxious.
Again, this just boils down to getting your spot earlier rather than later. Usually if you do that, everyone in your party will be able to see as well as the people around you.
3. Bring your own water bottles! Buying water in MK is expensive, just bring your own water bottles, and ask for cups of ice water which are normally free. Also, I recommend the Brita Water Filter bottles, so you can just ask for ice and get water from the water fountains, they work great and it saves some money.
Also, DRINK LOTS OF WATER, you don't want to be passing out on your vacation. Dehydration is a thing in Florida, especially when you are up and walking on your feet all day.
4. Always have an umbrella or a poncho, it could be perfectly sunny and then pouring rain 10 minutes later... Also, there is no button a cast member can press to turn off the rain. Sorry.
If it is raining, and the outdoor rides are closed, hit up the indoor ones. A lot of people just leave when it happens, but you should really stick it out. It's kind of fun if you don't mind being a little wet.
5. The 3 oClock parade is at precisely 3:00. But depending on where you are on the route, it could take a few minutes to get to your area, but yes, it DOES start at three p.m.
6. Cinnamon Rolls at Gaston's Tavern in New FantasyLand are a hidden gem. They're cheap and REALLY BIG. And also amazing.
7. Corn Dog Bites at Casey's Corner. That's all.