I'll start by saying that our Feb 2019 to Disney was the first vacation we spent a lot on since our honeymoon - air travel for 4, many days at the hotel park tickets, $3.50 waters, etc.  But it was a great trip and we loved it.

I love taking notes, so here are some brief, hopefully helpful notes on seeing the mouse.

6 months out you can make reservations for fun princess and character experiences (I believe start time at 6am).  We liked:
*Perfectly Princess Tea
*Cinderella's Royal Table
*Disney Hollywood Studios breakfast with Sofia and Doc McStuffins

Starting with this, I did it all through the Disney app (My Disney Experience), linked to our room reservation number (we stayed on resort - it's nice being on the monorail with the Magic Kingdom - you can do that with Grand Floridian, Polynesian, or The Contemporary)

Get the app.  You gotta just do it now.  We'll wait.  https://play.google.com/store/apps/details?id=com.disney.wdw.android

2 months out, you can start booking your Fast Pass.  As of Dec 2019, the timing is at 7am.   Some rides that we really needed it for were:
*Seven Dwarfs Mine Train (this is amazing - was my kids' first fast coaster and they loved it)
*Space Mountain (Lulu went on it!)
*Thunder Mountain (lots of fun!)
*Soarin' around the world (Epcot)
*Toy Story Mania (really fun target shooting game at Disneyworld Studios - though Slinky Dog looked good too)

You can go from the airport right to resort with Disney's Magical Express.  It's great - do it.  They take your checked bags right from the plane and they magically show up in your room.

Once in Orlando, we enjoyed:
*Rides in the morning - if you're staying at one of those hotels, you can show up at 8am and the lines are short; it's also not too hot then
*Eating at our hotel - we loved Gasparilla Island Grill (we also picked up snacks from there - hard boiled eggs, apple slices, carrots)
*Napping during the day
*Pool, then park and rides (note that if you spend your 3 fast passes in the morning, you can sign up for another tough to get ride at night - refresh by clicking the time button on the app)
*Watching the fireworks (at 8pm)

We also really enjoyed this food:
*Dinner at Be Our Guest (with the Beast - the food is amazing.  And we got to be late for a Fast Pass with the receipt from there!)
*Citrus Swirl ice cream in Adventure Land

Honorable Mention rides (worth doing once):
*Tea Cups (so much fun for our family!)
*It's a Small World ride
*The Carousel in Fantasy Land (Prince Charming Carousel)
*Peter Pan ride
*Dumbo and Aladdin Flying Carpet (very similar rides); spinning 15 ft in the air.
*Barnstormer (roller coaster for little ones)

We heard great things about, but didn't:
*Book a VIP Tour (front of line for rides, but super-expensive)
*Animal Kingdom
*Ordering food on the app and just picking up at the window
*Go to the castle just before the park opens for a daily princess opening ceremony

Other good things we did:
*Bought strollers
*Wore hats and sunblock (in February!)

Mistakes we made:
*Any time we tried to do too much
*Polynesian luau dinner isn't the best for young mousketeers
*Epcot is a lot for little ones, especially in a day with other things.  It's also not super-easy to get to.

There are lots of other resources too, like:

Updates from 2020 - again - it was super-magical!
1) We did "Early Morning Magic" and it was fantastic for a family of early risers.  In < 1.5 hours, we rode Seven Dwarfs Mine Train 4 times, and also went on pretty much every other ride that was open (Peter Pan, Winnie the Pooh, Dumbo).

2) We again stayed on Monorail and were there for the day of the Disney marathon (Feb 23).   It turns out lots of other people had trouble getting to the park because of road closures, so as monorail guests, we had a bunch of extra rides in the morning from 9am to 10:30am or so.  Not Seven Dwarfs, but a lot of the rest (w/o Fast Pass)

3) Gasparillo's remains the unsung hero of the dining options!

4) Princess Breakfast at Akershus was amazing and had a "Princess Procession".

5) I recommend avoiding the 50's Prime Time cafe - I know it's a shtick, but the wait staff comments were tough for my kids.

6) Liberty Tavern had a delicious lunch

7) The walk in the Epcot circle w/ countries is awesome