There are some of the changes I would have made to the film:
1. A Petrie hatching scene. It would have been a good scene to watch.
2. I would like the idea of Cera's real mom and sisters being alive. It was sad that they were never mentioned after the first film.
3. I've always liked the idea of Littlefoot having real siblings. (three nestmates and an older sibling)
4. I would have made Littlefoot's grandparents interact with him more instead of waiting till the 2nd film.
5. I would introduce Bron as Littlefoot's dad in the 1st movie instead of waiting till movie 10.
6. I like the idea of Spike having his real parents and maybe a sibling or two.
7. No silly terms like bright circle, mountains that burn (I like sun and volcano better).
8. Don't kill off Littlefoot's mom.
9. Have Littlefoot refer to his mom as Mom instead of Mother.
10. Instead of waiting till the 4th movie; I'd introduce Ali and her herd in the 1st movie.
11. I would not make Ali and her herd be related to Littlefoot's grandparents.
Those are my ideas for changes. Feel free to disagree; we all have our own opinions.