We took our son for his first visit at 14 month and we had the best time!
We went with the attitude that we would see what we could and not worry about what we missed. This was back when there were paper fast passes, so it is a bit different now that you have to plan so far out. It's awesome that you will have your parents along. With this new FP system you can take advantage of baby swap in conjunction with baby swap to essentially double your FP's.
I might consider taking along a stroller that reclines, the rental ones are really hard. It's kind of sad to see kids sleeping in them. Also, you will want to use the stroller beyond the parks. Our son would konk out in the stroller and we would stop for a drink or snack in a shady spot.
Plan a character meal, it's a much easier way to meet the character. Maybe show your daughter some videos of people seeing them so she can see how it goes. At that age DS2 was terrified, I have funny photos of him lunging away while I stood next to Buzz.
It's so easy to bring a toddler to Disney. It will be awesome for you to have that experience with your daughter and her grandparent! Have a super time!