If your toddlers like animals, I would go 2-3 days at AK. I would say only 1-2 days at EP, as there really isn't much for that age group there (unless they really like walking around the world showcase). Perhaps 1-2 days at HS. Again, not as much to do there with toddlers. At least 4 days at MK. There's a lot do do there with toddlers. Since you have hoppers, if the kiddos want to do a repeat of something at EP, but it won't take all day, you could go there in the morning and then hop to a different park in the afternoon or evening.
Perhaps take the approach of going to 1 park each day to see what your kiddos get into and want to do more of. I know it's harder to plan your trip taking this approach, but it might be more enjoyable for the kiddos if you kind of go-with-the-flow of what they seem to get into. I feel so bad for some kids when their parents are running around like crazy pulling them from one thing to the next, instead of giving the kids time to enjoy their surroundings. Disney does a really good job at creating things that kids are interested in, and it might be the last thing you would expect. For example, during our last trip we were standing in front of the water fountain in Epcot just watching the water show and enjoying the music. There was little girl that was just dancing and twirling about to the music. Nothing that was getting in the way of the others around her. Just doing her own thing. Mid-way through the song, the parents came and told her it was time to go and made her stop before the song was over. She left in tears. Perhaps, if they would've waited another 90 seconds for the song to finish, the little girl would've left happier (no guarantees of course).
I hope you have a fantastic trip!!!