You are awesome to worry about DD, but (and *please* don't take this the wrong way) unless you document every moment of this trip, frankly, she will remember very little about it - and that might be OK. I'm widely considered to be a "weird mom" because I refused to take *any* child to WDW before their 10th birthday; personally I think it's not always as much fun for babies and toddlers as we (the adults) think it is. They typically sit in strollers that are the closest thing down to the hot pavement all day, they can't really hear their loved ones over all the music and commotion going on, and they can't see them either, and then - to add insult to injury - as long as they are in the stroller, their view is primarily butts and ankles.
I'm *not* one of those grinchy people who says that babies and toddlers should be banned at Disney - far from it! But I just want you to remember for a minute that what she will mostly remember from this trip (if she is less than about 5 to 7 years old) will be the emotions associated with it, and not necessarily the kind of memories that an adult will form. So, she probably really won't remember much of her first trip on Peter Pan, or whatever her "first ride" is. Don't worry about knocking off rides on a bucket list - if you want her to have fun, let her lead the way. It may be that rides really aren't her thing at this age. And if *all* she wants to do is rides, well, you have been working a plan for that!
She won't "miss out" - she will still be at WDW, with you and the grands! She will be loved and happy and in a place where magical things happen all the time! There are smiley Cast Members who give you stickers, and smashed penny machines and you can get BUTTONS to wear that say "My First Trip" with your name on it! and then everyone says hi to you! There are Mickey Bars to eat and balloons to buy and so.much.popcorn! And if she doesn't ride Haunted Mansion on this trip, or if she never gets to do Flight of Passage until she's older... trust me, there are *far* worse things that could happen. She may be one of those littles who can't stand fireworks, or who is scared of the full-suit characters, but OK with the face characters. And she may be one of those kids who just wants to ride the boats and the train and the monorail and look at everything and then swim in the pool! I know that often families feel like they have to do "everything" on this one trip because (fill in the blank) and I respect that. But I also know from experience that trying to do WDW on a hard-and-fast-take-no-prisoners type of touring plan can result in widespread unhappiness and *bad* memories, and that's the opposite of what you want. Some of my families best trips have been the ones where we (literally) found out last minute that we could fly in to Orlando, and all of the ADRs were booked and all of the FPs were gone, and we had *more* fun than when we try to plan it all out perfectly!
One more thing to remember - many little kids never really understand how many rides there are at WDW, simply because so many of them are inside "show buildings" that house the entire ride, so there is no real visual cue about what is inside. Littles can *see* rides that are out in the open (like Dumbo or Barnstormer), but things like Peter Pan and Haunted Mansion (for example) you could quite possibly stroll right past, and she would never know. Shows like Mickey's Philharmagic, Monster's Inc Laugh Floor and Muppets 3D would also be great for her - (as well as you too!

) and there are many of those kinds of experiences all over all 4 of the Parks.
She will be happy because you are happy - and whatever it is that makes you laugh and smile will be great for her too. Enjoy this precious time, but remember that (aside from pictures and videos) eventually, she probably won't really remember WDW as much as she remembers the souvenirs you brought home. And she will remember the love.
With my whole heart, my wish for you and your sweet little girl is to have a *Magical* trip!