to use fastpass; I didn't see it in your post. This will help speed the process on more popular rides. If you need this defined more, just ask here. No one is prepared the first time on how long the lines are for the more popular rides. Pay attention to your wait times; although, they are not completely accurate they will still give you a guideline. You may want to skip one ride for the sake of going on three lesser rides. These are decisions you will need to make once you are doing it. Most people walk 6 to 12 miles a day at the parks depending on how long they stay in the parks. This can be tiring for first timers and you run out of steam. Pace yourself!
Next, be an early riser. Be aware getting into the parks have lines to get in; it's a little slow to do it. Bag checking and your passes take time to do. Watch for the entrances that have less people for getting in. The old saying is to go left when you can; everyone tends to go right. Work your way to the back of the park quickly as more and more people come in. The back of the park will be empty for a short moment for you to enjoy before the masses come. Take advantage of the extra magic hours especially the morning ones. We generally accomplish three times as much utilizing that extra morning hour.
Try to avoid bactracking; this is a huge waste of time. Do a loop around the park; this is how the parks where designed. There will be some backtracking with fastpass times and ADRs, but keep this to a minimum. The worse one is Animal Kingdom. You have to make a choice between the Safari ride and Expedition Everest for which to go to when you enter the park. One is left and one is right. Do not go back and forth to get to both rides in a row. That's just too much travelling time in the parks. Choose the one you want to do first and settle for the choice.
The first time will be somewhat overwhelming and I doubt everything will go as planned; so, just realize this is how it is, now. I agree with the other poster. Pick your absolutes and be reasonable.
I would automatically plan breaks into your schedule; so, you have down times; don't wait for a trigger to flare up. Don't be a commando. Plan breaks with shows, exhibits, eating, parades and so forth. Alternate your activities.
Be it that it's your first time, I doubt everything will go as planned. Come to realize this right now.
If you're flying in and using Magical Express for the first time you need to realize this is a slow process. You have to check in at ME and this takes a while. Getting a bus is not fast to the resort. The driver waits for it to be pretty full before leaving the airport. Right there you can lose time; because, you thought the process would go faster. There's a lot of walking at the Orlando airport to get where you need to go. If your not flying just ignore this info.
For the quiet places there are some choices like the first aid stations in each park. If there are some bad situations in a day this may not be so quiet, but it's pretty good most of the time. This would be my number one choice on getting away from everything. You can even ask for a cot and lay down for a while. In all the parks go to lesser attractions and slow it down some when you are feeling a trigger. You can still get to enjoy an attraction, but it won't be so crowded. In MK, I like the Tiki Room in Adventureland. The Stitch ride and the Monster show are ok in Tomorrowland to calm it down a bit. Country Bear Jamboree is a good one in Frontierland. My favorite is the River boat; this is a very calming ride. A walk behind the castle I like, too and there are character greets there, now. For AK, do the trails. The Tree of Life trail is quite relaxing and often not crowded. Go see the gorillas in Africa and the Tigers and bats in Asia. Rafiki's Planet is usually not as crowded as the rest of the park, but this is a time committment if you do it. It takes a long time to go back and forth from it. In Epcot, go to Innoventions in Future World. Universe of Energy ride is a good way to decompress. Living with the Land boat ride in the The Land Pavillon is a good one, but the Pavillon is always loaded with people; it's a big place. For World Showcase, go see a movie about a country: France, Canada and China are good choices, here. Enjoy some live steet acts that appear in the countries, too. For Hollywood Studios, I like One Man's Dream the best to slow it down. Another good one is The Art of Disney Animation and that has character greets in it. For a ride, the Backlot Express is a good one to do there.
Keep in mind park hopping takes time and sometimes it's not worth it. I find it somewhat disruptive; unless, I go back to the resort for a while and then go to the next park. Spending more time on buses is not my thing. In the end I don't think it's such an advantage.