If there is any way to add an EPCOT day, I would. My DD is 8 and has been going to WDW every year since she was 2. EPCOT has always been by far her favorite park other than MK- it is a 2 day park for us. It has the Nemo Ride, Turtle Talk with Crush, Living with the Land, Soarin, the boat ride in Mexico, the Agent P (Phineas and Ferb) missions, Kidcot stations, Pick a Pearl (if you want to pay to do that), a ton of Princesses and other characters out for meet and greets, a ton of entertainers like jugglers, balancing acts, bands, drummers, acrobats, and so much more. She ranks eating at Biergarten (with a dance floor and German polka band) right up there with Princess meals. I can't imagine skipping EPCOT with her. We've gone to DL once a year for the last 4 years too, and when we do, the only thing she complains about missing from WDW is EPCOT.
I think you have made some good dining choices for that age. We don't do Rainforest at WDW because there is one by my in-laws home only 2 1 /2 hours from us, so we hit that one at least a couple of times a year, but I'm assuming the WDW one is like it and is really fun. As far as dining at DHS, it really isn't a great dining place. We like to actually for one day have a semi-quiet meal (as opposed to characters, bands, crowds etc), so we tend to do Mama Melrose. 50s Prime Time can be fun (it is like a 50s kitchen where the servers act like you are family and may get onto you for not cleaning your plate etc- and which serves "home" food like fried chicken, pot roast, and meatloaf). Some people love Sci-Fi- but we have not been there because we looked at it on the internet and DD was not a fan of the sci fi clips. There is a Disney Jr. character meal there, we haven't done it and I've heard mixed reviews.
As far as the other parks things DD loved at that age:
MK
Peter Pan was the absolute favorite ride
Small World
Pooh
Philharmagic
Ariel's Grotto to meet Ariel with her tail
Any and all character meet and greets
Barnstormer
Dumbo
There is a water play area over by Dumbo/Barnstormer
Tea Cups
Buzz Lightyear ride
Monster's Inc. Laugh Floor
Aladdin's Magic Carpets
Jungle Cruise
Tikki Room
Never underestimate the appeal of the Tommorowland Transit Authority Peoplemover
Enchanted Tales with Belle and Ariel's ride were not around until DD was 6, but she still loved them and 4 or 5 year olds too.
Same with a lunch at Be Our Guest if you don't have dinner reservations there- it is very impressive inside.
Your GDs will likely be tall enough to ride any of the thrill rides that they like. My DD turned out to not be much of a thrill seeker. Splash Mountian is a water ride where they might either get a drop of water on them at the end or get soaked. My DD isn't a big fan of it because she is terrified on the last drop. She does like Space Mountain though. She isn't a fan of Big Thunder because it is too jerky. If your girls are thrillseekers they may love them all.
I love Pirates of the Carribean, but DD is just okay with it.
She will ride Haunted Mansion, but she isn't a big fan as it creeps her out a little.
If the Seven Dwarves Mine Train is open by your trip-that will be a huge draw (with huge crowds).
DHS
Toy Story Mania
Star Tours
Beauty and the Beast Show
Little Mermaid Show
Muppets 3D
Character meet and greets- Phineas and Ferb; Buzz and Woody; Sophia etc.
These were pretty much DD's only must dos at DHS at that age. At age 4 and 5- DHS would have been a half day park for us except we were usually there during the Christmas lights.
Your girls might like Fantasmic in the evening- my DD prefers the DL version (so do DH and I), so we don't usually spend the time in line for the WDW version.
At age 4, the Disney Jr. show might still have been a must do- if the 5 year old likes Princess Sophia it may be a must do for her too as they recently added a Disney Jr. section. That is the only show that DH and I don't find particularly enjoyable at Disney.
There is an "unpublished" thing fans call "character Palooza" which is not a given, but usually occurs about4 1/2 hours before the last Fantasmic show begins. This is when several characters come out and spend about 20 minutes doing meet and greets on the Streets of America (on San Francisco Street). Here is a guide from Kenny the Pirate on that:
http://kennythepirate.com/category/character-palooza-2/
Kenny is a great resource for all character schedules etc.
The Great Movie Ride - DD thinks is okay. She has never been scared on it (I cover her eyes during the Alien part), but I have seen kids get scared.
DD started liking the Indiana Jones Stunt show at age 6.
She won't even consider trying Tower of Terror.
Your girls probably won't be tall enough for RNRC
Animal Kingdom:
DD has never cared a whole lot for AK- I think part of the reason is that we have a really good zoo at home, so she wants Princesses (which AK has no Princess presence except for Pochahontas), and does not want to stand and look at the same kind of animals she can stand and look at 20 minutes from our house. If you don't have a great zoo at home, it might be a huge hit.
Her only must dos there are a character meal at Tusker House, riding Safari, seeing the Lion King show, and meeting some characters. By noon, she is usually begging to leave there and go back to MK or EPCOT. I'm the only one in the family that really likes AK and could probably happily spend a whole day there. I don't ever get to because DD and DH are always wanting to leave!
That said- in 2013 AK started a thing called Wilderness Explorers where you get a field guide book from a ranger at a ranger station and then you have to earn badges (sticker badges placed in the book by a ranger) throughout the park to fill the book. The book has over 30 badges you can earn. Sometimes you do an activity and then report to the ranger station to get your badge. Other times you report to a ranger and they give you information or lead you through an activity to get a badge. At age 7 last year, DD loved that. For the first time, she actually showed some interest in AK and we spent a good part of the day there. Your girls might be the same way.