First of all, don't panic! You'll have an amazing time.
I would definitely work on the assumption you'll want to take a break in the middle of the day and leave time to head back to the hotel for a nap or a swim. We usually pick up some simple breakfast and lunch things on our way from the airport (bagels, cream cheese, crisps, fruit etc) or get it delivered to the hotel before we arrive. We keep these in our room fridge so we can collapse in the shade without having to run round and deal with breakfast / lunch crowds etc. Sometimes on our Animal Kingdom days we head to the Animal Kingdom Lodge instead of back to our hotel as it's closer, the main lobby is stunning, and you can hang out and watch the animals for a bit.
Secondly, I wouldn't get too stuck on booking lightning lanes. The only park I would say it's really important to book for is your magic kingdom day. For the others, provided you're happy to get up in plenty of time for early opening (as hotel guests you will have access to this), you'll likely have the biggest rides knocked out during this so it's a bit of an unnecessary expense. You should arrive AT LEAST half an hour before the official start of Early Theme Park Entry - Hollywood Studios for example often actually lets park guests in at this point. We usually aim for an hour - 45 minutes, and bring breakfast and a book with us so we're at the very front or near the front of the turnstile lines to get in.
It might also be worth purchasing for the day you go to the waterpark, as you can then pre-stack rides for whichever park you go to in the evening.
I think only three rides now use virtual lines: Tiana's Bayou, Guardians of the Galaxy, and Tron. Worth setting an alarm just before the lines open and have each member of your party on a different phone trying to get a slot. I don't think we've ever had one of us not get it. Guardians is by far the best of the three - I honestly wouldn't be that fussed about Tiana. Tron is fun but literally only lasts a minute (and makes my back hurt).
Restaurant bookings - great if you can get them. If not it's worth checking a few times a couple of days / the day before / the day that you want to go as a lot of people will release slots at that point. Would 100% recommend Homecomin' as the no.1 Disney Springs pick. We've never got a reservation, but just pitched up, asked to be added to the standby line, and window shopped while we waited. You don't need reservations for quick service restaurants, and you can also do mobile orders through the Disney app (though look to order about a half hour before you want to eat).
There are lots of lovely things to do outside the parks as well so if you're feeling overwhelmed while you're there or want a break from things you need to book you can always do one of them. One of our favourite things is to watch the Electrical Water Pageant and then the Magic Kingdom fireworks from the beach at the Polynesian - you'll likely want to see the projections on the castle the first time but this is great for repeat (and much, much more relaxed) viewings.
If you're really feeling overwhelmed then sites like Touring Plans will create a suggested itinerary for you (and their crowd calendar is useful for choosing which day to do which park). Others have already recommended the Tom Bricker plans though and these are also pretty good (and free) if you're happy to do a bit more research yourself. And the Dibb forums are a great resource!