We planned ahead in the sense that we knew roughly what was in each park that we'd like to go on and what dd was too short to go on in advance. You can take food and drink into Disney, w didn't do universal as dd too short for too many things there yet, so will go back Ina few years.
Fireworks/light show in Epcot was great. We saw Main Street parade in magic kingdom which was ok. Spent a long morning each in the water parks and popped into a kingdom after for a couple of tides and dinner. Didn't book meals ahead but while not cheap, the places to walk. Up. We're ok.
Look out for hidden mickeys in all parks.
In animal kingdom, there's a wilderness ranger trail to follow and get stickers around the park. GET A book AT&T he bridge just after entry. Rangers like in Up.
In Epcot, grab a bear that you bring to each country to get a stamp and have a chat with people there. Duffy bear.
I think there's a trail if some sorts in magic kingdom and Hollywood studios too. But we never found them. They are all free (but some make you go into shops for some stamps or stickers, animal kingdom less so).
Bring a notebook and fat Marker for autographs.
We didn't plan a route of rides, just picked as we passed mostly. Get a map from guest services as you arrive in each park, very very useful. GET a few so kids can look too and plan. AND SPot water and food spots on them too.
Be prepared for meltdowns in all, even adults. Take breaks, be prepared to go home early some days. If you go early, head back to hotel for break, swim, nap even, and back to park in evening if you want, or just bowling in downtown Disney. Don't overload yourselves. Drink lots of water, it's very humid and you won't notice it iced water in cups is free in most food spots.
Enjoy!!